TRS-80 DOS - NEWDOS/80 v2.0 for the Model I - SYS6/SYS Disassembled

Call subroutine at 5881H to display the error message to the user.

5246

Call the DOS print message routine at 4467H to output the message.

5249

LD HL,4030H 21 30 40

Load HL with 4030H, a return address or continuation point.

524C

JR 5222H 18 D4

JUMP back to 5222H to retry the error exit sequence.

524EH - Format Buffer Initialization

This routine initializes the format buffer by loading the current buffer pointers and preparing for the track data relocation.

524E

LD HL,(5D14H) 2A 14 5D

Load HL with the buffer end pointer from 5D14H. This marks where the track buffer data currently ends.

5251

LD DE,(5D12H) ED 5B 12 5D

Load DE with the buffer start pointer from 5D12H. This marks where the track buffer data begins.

5255

OR A B7

Clear the Carry flag to prepare for a 16-bit subtraction. This ensures SBC HL,DE will calculate the true difference without borrowing.

5256

SBC HL,DE ED 52

Subtract DE from HL: HL = (5D14H) - (5D12H). This calculates the size of the data block that needs to be relocated. The result in HL is the byte count.

5258

LD B,H 44

Copy the high byte of the block size to Register B. BC will hold the byte count for the LDIR instruction.

5259

LD C,L 4D

Copy the low byte of the block size to Register C. Now BC = block size for the upcoming block move.

525A

PUSH DE D5

Save the original start pointer (5D12H contents) on the stack. This will be the source address for the LDIR block copy.

525B

LD HL,5D16H 21 16 5D

Load HL with 5D16H, the new destination address for the track buffer data. This is where the data will be relocated to.

525E

LD (5D12H),HL 22 12 5D

Update the start pointer at 5D12H to point to the new location (5D16H). The buffer's base address is now updated.

5261

PUSH HL E5

Save the new start address (5D16H) on the stack for later use.

5262

EX DE,HL EB

Exchange DE and HL. Now DE = 5D16H (destination) and HL is free for the source address.

5263

LDIR ED B0

Block copy: Move BC bytes from (HL) to (DE), incrementing both pointers. This relocates the track buffer data from its old location to 5D16H.

5265

LD (5D14H),DE ED 53 14 5D

Update the end pointer at 5D14H to the new end position after the block move. DE now points past the last byte copied.

5269

Call the format preparation subroutine at 5578H. This initializes additional format parameters.

526C

POP HL E1

Restore the new buffer start address (5D16H) from the stack into HL.

526D

CALL 56A6H CD A6 56

Call the format status check subroutine at 56A6H. This checks if the format operation should continue. Returns Z flag if complete.

5270

JP Z,552DH CA 2D 55

If the Z flag is set (format complete or no more work), JUMP to 552DH to finalize the format operation.

Format is not complete - display status and calculate how many tracks can be formatted with available memory.

5273

LD HL,627BH 21 7B 62

Load HL with the address of a status message at 627BH to display formatting progress.

5276

CALL 587EH CD 7E 58

Call the message display subroutine at 587EH to show the formatting status to the user.

5279

LD HL,(593CH) 2A 3C 59

Load HL with the memory limit stored at 593CH. This is the high memory boundary for the format buffer.

527C

LD DE,(5D14H) ED 5B 14 5D

Load DE with the current end pointer from 5D14H (where track data ends).

5280

OR A B7

Clear the Carry flag for subtraction.

5281

SBC HL,DE ED 52

Calculate HL = memory limit - current position. This gives the available memory remaining for track formatting.

5283

LD DE,0102H 11 02 01

Load DE with 0102H (258 bytes). This is the size of one track entry in the format table (256 bytes of sector data + 2 bytes overhead).

5286

LD A,FFH 3E FF

Initialize Register A to FFH (-1). The following loop will count how many tracks can fit.

[LOOP START] - Count how many track entries (258 bytes each) can fit in the remaining memory.

5288

INC A 3C

Increment the track counter in Register A. First iteration makes it 00H.

5289

OR A B7

Clear the Carry flag for the next subtraction.

528A

SBC HL,DE ED 52

Subtract one track entry size (258 bytes) from the remaining memory in HL.

528C

JR NC,5288H 30 FA

If no borrow (memory still available), [LOOP] back to 5288H to count another track. Continue until we run out of space.

[LOOP END] - Register A now contains the number of tracks that can be formatted in one batch.

528E

LD (531AH),A 32 1A 53

Store the track batch count in the self-modifying code location at 531AH. This will be used as the loop limit.

5291

LD HL,594CH 21 4C 59

Load HL with address 594CH, which holds the source drive number for the format operation.

5294

CALL 5538H CD 38 55

Call subroutine at 5538H to set up the drive for the format operation based on the drive number at (HL).

5297

XOR A AF

Clear Register A to zero. This initializes the track counter for the upcoming format loop.

5298

LD HL,(5D14H) 2A 14 5D

Load HL with the current track table end pointer from 5D14H. New track entries will be added here.

529B

JR 5316H 18 79

JUMP forward to 5316H to enter the main track formatting loop at the loop test point.

529DH - Main Track Formatting Loop

[MAIN LOOP START] - This loop reads each track from the source disk and stores it in the track buffer. Each iteration handles one track.

529D

PUSH HL E5

Save the current track table pointer on the stack. HL points to where this track's data will be stored.

529E

INC HL 23

Increment HL past the first byte of the track entry (track number marker).

529F

INC HL 23

Increment HL again past the second byte (status byte). HL now points to the sector data area.

52A0

LD (5AE8H),HL 22 E8 5A

Store this address at 5AE8H as the destination buffer for the upcoming disk read operation.

52A3

LD A,80H 3E 80

Load Register A with 80H (128), the read sector command flag for the disk operation.

52A5

LD (57EBH),A 32 EB 57

Store the command flag at 57EBH. This location controls the disk I/O operation type.

52A8

Call the disk read subroutine at 57C8H to read the current track's sectors from disk. Returns status in A.

52AB

JR Z,52CFH 28 22

If Z flag set (successful read), JUMP to 52CFH to continue with the next step.

52AD

CP 06H FE 06

Compare the error code with 06H (Record Not Found). This error is expected for unformatted tracks.

52AF

JR Z,52D0H 28 1F

If Record Not Found error, JUMP to 52D0H to handle the unformatted track case.

52B1

CP 1CH FE 1C

Compare with error code 1CH (End of Data on track).

52B3

JR Z,52B9H 28 04

If End of Data, JUMP to 52B9H to check if this is a COPY operation that needs special handling.

52B5

CP 1DH FE 1D

Compare with error code 1DH (End of Track encountered).

52B7

JR NZ,52CAH 20 11

If NOT End of Track error, JUMP to 52CAH to handle the error and possibly retry.

Error 1CH or 1DH occurred - check if COPY option is set which requires special end-of-track handling.

52B9

LD HL,0000H 21 00 00

Load HL with 0000H. This will be used to signal end-of-disk if COPY mode confirms completion.

52BC

LD A,(5996H) 3A 96 59

Load the option flags byte 3 from 5996H to check the COPY option status.

52BF

AND 08HAND 00001000 E6 08

Mask with bit 3 to test the COPY option flag. Z flag set if COPY is NOT active.

52C1

CALL NZ,56A2H C4 A2 56

If COPY option IS active (NZ), CALL 56A2H to verify this is a valid end-of-disk condition.

52C4

JP Z,549CH CA 9C 54

If confirmed as end-of-disk (Z set), JUMP to 549CH to finish the copy operation.

52C7

POP HL E1

Restore the track table pointer from the stack.

52C8

JR 529DH 18 D3

[LOOP] - Jump back to retry reading this track from the beginning.

Disk error occurred that wasn't an expected end condition - attempt error recovery.

52CA

Call the error handler at 585AH. This displays the error and asks user to retry or abort.

52CD

JR NZ,52A8H 20 D9

If user chose to retry (NZ), JUMP back to 52A8H to attempt the disk read again.

Read succeeded (or user chose to skip) - store the track entry in the buffer.

52CF

XOR A AF

Clear Register A to zero. This indicates a successful read with no error code.

52D0H - Store Track Entry in Buffer

At this point, either the track was read successfully (A=00) or a "Record Not Found" error occurred (A=06), indicating an unformatted track. The code stores the track marker and status in the track table.

52D0

POP HL E1

Restore the track table pointer from the stack. HL points to the start of this track's entry.

52D1

LD (HL),FFH 36 FF

Store FFH as the track marker byte. This indicates a valid track entry in the format buffer.

52D3

INC HL 23

Advance to the status byte position in the track entry.

52D4

LD (HL),A 77

Store the read status in Register A (00=success, 06=not formatted). This records whether the track had readable data.

52D5

INC HL 23

Advance HL to point past the status byte, to the sector data area of this track entry.

52D6

Call subroutine at 571BH to update the track number and advance to the next track position on disk.

52D9

PUSH HL E5

Save the current position (pointing into sector data) on the stack.

52DA

EX DE,HL EB

Move the sector data pointer to DE. This will be the destination for any boot sector copy.

52DB

LD A,(5996H) 3A 96 59

Load the option flags byte 3 from 5996H to check format options.

52DE

AND 0CH E6 0C

Mask with bits 2-3 (COPY and BACKUP options). Z flag set if neither option is active.

52E0

JR NZ,5311H 20 2F

If COPY or BACKUP option is set (NZ), skip the boot sector logic and JUMP to 5311H.

FORMAT only (no COPY/BACKUP) - check if this is track 0 and if we need to copy the boot sector template.

52E2

LD A,(5994H) 3A 94 59

Load the option flags byte 1 from 5994H.

52E5

BIT 1,A CB 4F

Test bit 1 - the "skip boot sector" option. Z flag set if boot sector should be included.

52E7

JR NZ,5311H 20 28

If skip boot sector flag is set (NZ), JUMP to 5311H to bypass boot sector copying.

52E9

LD HL,(5AEFH) 2A EF 5A

Load HL with the current track number from 5AEFH (stored as 16-bit value).

52EC

DEC HL 2B

Decrement to get track-1 (so track 0 becomes FFFFH when checked, but track 1 becomes 0000H).

52ED

LD A,H 7C

Load the high byte of (track-1) into A.

52EE

OR A B7

Test if high byte is non-zero. If track was 0, H would be FFH after DEC, so this would be NZ.

52EF

JR NZ,5311H 20 20

If high byte non-zero, this is not track 0 or 1, JUMP to 5311H to skip boot sector copy.

52F1

LD A,L 7D

Load the low byte of (track-1) into A.

52F2

CP 02H FE 02

Compare with 02H. If track was 0, L=FFH (NC). If track was 1, L=00H (C). If track was 2, L=01H (C).

52F4

JR NC,52FEH 30 08

If L >= 02H (No Carry), JUMP to 52FEH. This happens for track 0 (L=FFH), or tracks 3+.

Track 1 or 2 - copy the directory boot sector template from 64BAH.

52F6

LD HL,64BAH 21 BA 64

Load HL with 64BAH, the address of the directory boot sector template.

52F9

CALL 5C80H CD 80 5C

Call subroutine at 5C80H to set up BC with the sector size (256 bytes) for the copy operation.

52FC

JR 530FH 18 11

JUMP to 530FH to perform the LDIR copy of the boot sector template.

Check if this is track 0 and if the track data contains a valid boot sector signature.

52FE

JR NZ,5311H 20 11

If L != 02H after earlier compare (meaning not track 0), JUMP to 5311H to skip.

5300

LD HL,00EFH 21 EF 00

Load HL with offset 00EFH (239). This is the location of the boot sector signature within the sector.

5303

ADD HL,DE 19

Add the sector data base address (DE) to get the absolute address of the signature byte.

5304

LD A,(HL) 7E

Load the byte at the signature position.

5305

CP A5H FE A5

Compare with A5H, the NEWDOS/80 boot sector signature. Z flag set if valid signature found.

5307

JR NZ,5311H 20 08

If signature invalid (NZ), JUMP to 5311H - don't copy the boot sector overlay.

Valid NEWDOS/80 boot sector found - copy the 16-byte boot overlay from 6EB5H.

5309

LD HL,6EB5H 21 B5 6E

Load HL with 6EB5H, the address of the boot sector overlay data (16 bytes).

530C

LD BC,0010H 01 00 10

Load BC with 0010H (16), the number of bytes to copy from the overlay.

530F

LDIR ED B0

Block copy BC bytes from (HL) to (DE). Copy the boot sector template or overlay to the track buffer.

5311

POP HL E1

Restore the sector data pointer from the stack.

5312

INC H 24

Increment H to advance HL by 256 bytes, moving to the next track entry in the buffer.

5313

LD A,00H 3E 00

Load A with 00H. Note: This is self-modifying code - the immediate value at 5314H is updated at runtime.

5315

INC A 3C

Increment the track counter in A.

5316

LD (5314H),A 32 14 53

Store the updated track counter back to 5314H (the immediate value in the LD A,nn instruction above).

5319

CP 0AH FE 0A

Compare track counter with 0AH. Note: The 0AH at 531AH is also self-modifying - set at 528EH to the batch size.

531B

JP C,529DH DA 9D 52

If counter < batch limit (Carry set), [LOOP] back to 529DH to process the next track.

[BATCH COMPLETE] - All tracks in this batch have been read. Now write them to the destination disk.

531E

CALL 5324H CD 24 53

Call the batch write subroutine at 5324H to write all buffered tracks to the destination disk.

5321

JP 5291H C3 91 52

JUMP back to 5291H to set up and process the next batch of tracks.

5324H - Write Track Batch to Destination

This subroutine writes all the tracks that were read into the buffer to the destination disk. It handles COPY/BACKUP modes which may write to a different drive.

5324

CALL 5535H CD 35 55

Call subroutine at 5535H to switch to the destination drive for writing.

5327

LD A,(5314H) 3A 14 53

Load the track counter from 5314H (number of tracks that were read in this batch).

532A

OR A B7

Test if the track counter is zero. Z flag set if no tracks were read.

532B

RET Z C8

If no tracks to write (Z), RETURN immediately - nothing to do.

532C

LD HL,(5D14H) 2A 14 5D

Load HL with the current buffer end pointer from 5D14H. This points past the last track entry.

532F

LD (544FH),HL 22 4F 54

Store this end pointer at 544FH for later reference during the write loop.

5332

LD DE,(5B21H) ED 5B 21 5B

Load DE with the remaining granule count from 5B21H (used for space tracking in COPY/BACKUP).

5336

LD (5401H),DE ED 53 01 54

Store this value at 5401H for use in the write operation tracking.

533A

XOR A AF

Clear Register A to zero.

533B

LD (53ECH),A 32 EC 53

Initialize the write status flag at 53ECH to zero (no writes performed yet).

533E

PUSH HL E5

Save the current buffer pointer on the stack.

533F

LD A,(5996H) 3A 96 59

Load the option flags byte 3 from 5996H to check COPY/BACKUP settings.

5342

AND 0CH E6 0C

Mask with bits 2-3 (COPY=08H and BACKUP=04H options). Z if neither set.

5344

JP Z,53D5H CA D5 53

If pure FORMAT (no COPY/BACKUP), JUMP to 53D5H to perform a simple write.

5347

AND 08HAND 00001000 E6 08

Test bit 3 specifically - the COPY option. Z if this is BACKUP (not COPY).

5349

JR Z,5360H 28 15

If BACKUP mode (bit 3 clear), JUMP to 5360H to handle BACKUP-specific logic.

COPY mode - verify source and destination tracks match before writing.

534B

LD A,(HL) 7E

Load the track marker byte from the current buffer entry.

534C

CP (IX+07H) DD BE 07

Compare with the destination track number at IX+07H. Checks if source and destination tracks are aligned.

534F

JR Z,5360H 28 0F

If tracks match (Z), JUMP to 5360H to proceed with the write.

Track mismatch in COPY - need to seek to correct track on destination before writing.

5351

PUSH AF F5

Save the source track number (from the buffer entry) on the stack.

5352

CALL 53FBH CD FB 53

Call subroutine at 53FBH to finalize any pending write operations.

5355

POP AF F1

Restore the source track number to Register A.

5356

LD IX,5B17H DD 21 17 5B

Load IX with 5B17H, the address of the destination drive control block.

535A

CALL 56B9H CD B9 56

Call subroutine at 56B9H to seek to the specified track on the destination drive.

535D

POP HL E1

Restore the buffer pointer from the stack.

535E

JR 532FH 18 CF

JUMP back to 532FH to retry the write with the destination now on the correct track.

5360H - COPY/BACKUP Granule Allocation Check

This section handles space allocation for COPY and BACKUP operations. It checks if there's room on the destination disk before writing.

5360

LD HL,(5B21H) 2A 21 5B

Load HL with the remaining granule count from 5B21H for the destination disk.

5363

LD A,H 7C

Load the high byte of the granule count into Register A.

5364

OR L B5

OR with the low byte. Z flag set if remaining granules = 0000H (disk full or newly formatted).

5365

JR NZ,53D5H 20 6E

If granules remaining (NZ), JUMP to 53D5H to proceed with the write operation.

No granules allocated yet - need to request allocation from destination disk's directory.

5367

XOR A AF

Clear Register A to zero.

5368

LD (53D7H),A 32 D7 53

Store zero at 53D7H (the self-modifying location in the write loop). This initializes the retry flag.

536B

LD A,(5996H) 3A 96 59

Load the option flags byte 3 from 5996H.

536E

BIT 3,A CB 5F

Test bit 3 - the COPY option flag. Z if BACKUP mode, NZ if COPY mode.

5370

PUSH HL E5

Save the granule count (0000H) on the stack.

5371

LD HL,(5AF1H) 2A F1 5A

Load HL with the source disk's total granules from 5AF1H (for BACKUP mode default).

5374

LD A,(5AEDH) 3A ED 5A

Load Register A with the source disk type byte from 5AEDH.

5377

JR Z,537FH 28 06

If BACKUP mode (Z flag from bit test at 536E), JUMP to 537FH to use source disk values.

COPY mode - use destination disk's granule parameters instead of source.

5379

LD HL,(5B23H) 2A 23 5B

Load HL with the destination disk's total granules from 5B23H.

537C

LD A,(5B1FH) 3A 1F 5B

Load Register A with the destination disk type byte from 5B1FH.

537F

OR A B7

Test the disk type byte. Z if zero (standard single-density disk).

5380

JR NZ,5383H 20 01

If non-zero disk type (NZ), JUMP to 5383H to skip the decrement.

5382

DEC HL 2B

Decrement the granule count by 1. For standard disks, adjust for system granule reservation.

5383

LD A,H 7C

Load high byte of the granule count into A.

5384

AND L A5

AND high and low bytes together. Result is FFH only if both bytes are FFH.

5385

INC A 3C

Increment A. If HL was FFFFH (no granules available), A becomes 00H and Z flag is set.

5386

JR Z,53D1H 28 49

If no granules available (Z), JUMP to 53D1H to skip allocation and continue.

5388

LD (5B21H),HL 22 21 5B

Store the granule count at 5B21H as the number of granules to allocate for this operation.

538B

LD HL,436BH 21 6B 43

Load HL with 436BH, the address of the DOS control byte in the work area.

538E

SET 1,(HL) CB CE

Set bit 1 of the control byte to enable special allocation mode for the upcoming disk operation.

5390

CALL 57CEH CD CE 57

Call the disk allocation subroutine at 57CEH to request granules from the destination disk.

5393

RES 1,(HL) CB 8E

Reset bit 1 of the control byte to restore normal operation mode.

5395

JR Z,53D1H 28 3A

If allocation failed or no space (Z), JUMP to 53D1H to handle the error condition.

Allocation returned an error - check if it's a recoverable condition.

5397

PUSH AF F5

Save the error code on the stack.

5398

LD HL,5995H 21 95 59

Load HL with address 5995H (option flags byte 2).

539B

BIT 7,(HL) CB 7E

Test bit 7 - the "abort on error" flag. NZ if abort is requested.

539D

JR NZ,53ADH 20 0E

If abort flag set (NZ), JUMP to 53ADH to display error and abort.

539F

LD HL,5996H 21 96 59

Load HL with address 5996H (option flags byte 3).

53A2

BIT 2,(HL) CB 56

Test bit 2 - the BACKUP flag. NZ if BACKUP mode is active.

53A4

JP NZ,521EH C2 1E 52

If BACKUP mode (NZ), JUMP to the error handler at 521EH. BACKUP errors are more serious.

53A7

SUB 1AH D6 1A

Subtract 1AH (26) from the error code. Adjusts error code for comparison.

53A9

CP 02H FE 02

Compare adjusted error with 02H. Checks if error is 1AH or 1BH (disk full conditions).

53AB

JR C,53B3H 38 06

If error 1AH or 1BH (Carry set), JUMP to 53B3H to handle disk full gracefully.

53AD

CALL 5868H CD 68 58

Call error display subroutine at 5868H to show the disk error to the user.

53B0

JP 521EH C3 1E 52

JUMP to the error handler at 521EH to abort the operation.

Disk full condition - finalize the partial copy and prepare to complete.

53B3

CALL 56DDH CD DD 56

Call subroutine at 56DDH to get the directory entry address for the file being written.

53B6

INC HL 23

Advance to the first data field in the directory entry.

53B7

INC HL 23

Advance to the second data field.

53B8

INC HL 23

Advance to the third field - the file attributes byte.

53B9

XOR A AF

Clear Register A to zero.

53BA

LD (HL),A 77

Clear the file attributes byte to indicate the file is incomplete or needs attention.

53BB

LD DE,0011H 11 11 00

Load DE with 0011H (17), the offset to the granule allocation area of the directory entry.

53BE

ADD HL,DE 19

Add offset to HL to point to the first granule pointer in the directory entry.

53BF

LD (HL),A 77

Clear the first granule pointer (set to 00H indicating no allocation yet).

53C0

INC HL 23

Advance to the next byte in the directory entry.

53C1

LD (HL),A 77

Clear the second byte of the granule allocation.

53C2

CALL 5711H CD 11 57

Call subroutine at 5711H to write the updated directory entry back to disk.

53C5

POP HL E1

Discard the saved error code from the stack (was pushed at 5397H).

53C6

LD HL,5AD8H 21 D8 5A

Load HL with 5AD8H, the address of a "disk full" message.

53C9

CALL 586FH CD 6F 58

Call subroutine at 586FH to display the disk full notification to the user.

53CC

LD A,FFH 3E FF

Load Register A with FFH to set the "disk full encountered" flag.

53CE

LD (53D7H),A 32 D7 53

Store FFH at 53D7H (the self-modifying location) to flag that disk is full.

53D1

POP HL E1

Restore the granule count value from the stack (pushed at 5370H).

53D2

LD (5B21H),HL 22 21 5B

Store the granule count back at 5B21H.

53D5H - Write Track to Destination Disk

This is the actual track write section. It processes each track in the buffer and writes it to the destination disk.

53D5

POP HL E1

Restore the track buffer pointer from the stack (pushed at 533EH). HL points to current track entry.

53D6

LD A,00H 3E 00

Load A with 00H. Note: This is self-modifying code at 53D7H - updated to FFH when disk is full.

53D8

OR A B7

Test the disk full flag. Z if no disk full condition, NZ if disk is full.

53D9

JR Z,53DFH 28 04

If disk not full (Z), JUMP to 53DFH to proceed with writing.

53DB

CALL 585EH CD 5E 58

Call subroutine at 585EH to display a status message (disk full warning during write).

53DE

DEC A 3D

Decrement A. If A was 01H (from skip), Z flag will be set.

53DF

CALL Z,546DH CC 6D 54

If Z flag set (write needed), CALL 546DH to perform the actual sector write operation.

53E2

INC HL 23

Advance HL past the track marker byte.

53E3

JR Z,53E6H 28 01

If the write was successful or skipped (Z), JUMP to 53E6H to skip storing status.

53E5

LD (HL),A 77

Store the write status/error code in the track entry's status byte.

53E6

INC HL 23

Advance HL past the status byte.

53E7

INC H 24

Increment H to advance HL by 256 bytes, moving to the next track entry in the buffer.

53E8

Call subroutine at 571BH to update the track counter and position for the next track.

53EB

LD A,00H 3E 00

Load A with 00H. Note: This is self-modifying code at 53ECH - the write counter.

53ED

INC A 3C

Increment the write counter.

53EE

LD (53ECH),A 32 EC 53

Store the updated write counter back at 53ECH.

53F1

LD A,(5314H) 3A 14 53

Load the remaining track count from 5314H (how many tracks left to write in this batch).

53F4

DEC A 3D

Decrement the remaining track count.

53F5

LD (5314H),A 32 14 53

Store the updated count back at 5314H.

53F8

JP NZ,533EH C2 3E 53

If tracks remaining (NZ), [LOOP] back to 533EH to write the next track.

53FBH - Finalize Write Batch

This subroutine is called when a write batch is complete or when switching tracks during COPY. It ensures all pending operations are completed.

53FB

LD A,(53ECH) 3A EC 53

Load the write counter from 53ECH (number of tracks successfully written).

53FE

OR A B7

Test if any tracks were written. Z flag set if counter is zero.

53FF

RET Z C8

If no tracks were written (Z), RETURN immediately - nothing to finalize.

5400H - Post-Write Verification Loop

After writing tracks to the destination disk, this code performs verification by reading back the data to ensure it was written correctly. This is part of the FORMAT/COPY/BACKUP verification phase.

5400

LD HL,0000H 21 00 00

Load HL with 0000H. Note: This is self-modifying code at 5401H - updated with granule count at 5336H.

5403

LD (5B21H),HL 22 21 5B

Store the granule count at 5B21H to restore the original value for the next batch.

5406

LD HL,(5D10H) 2A 10 5D

Load HL with the sector data pointer from 5D10H for the verification read.

5409

LD (5B1AH),HL 22 1A 5B

Store this pointer at 5B1AH for the disk I/O routine to use as the buffer address.

540C

LD A,20H 3E 20

Load Register A with 20H, the verify/read-after-write command flag.

540E

LD (57EBH),A 32 EB 57

Store the command flag at 57EBH to set the operation mode to verify.

5411

LD HL,(544FH) 2A 4F 54

Load HL with the track buffer end pointer from 544FH (saved at 532FH).

5414

INC HL 23

Advance to the status byte of the current track entry.

5415

LD A,(HL) 7E

Load the track status byte into Register A.

5416

INC A 3C

Increment A. If status was FFH (end marker), A becomes 00H and Z flag is set.

5417

CALL Z,585EH CC 5E 58

If end marker found (Z), CALL 585EH to display appropriate status message.

541A

JR Z,544EH 28 32

If end marker found (Z), JUMP to 544EH to finish this verification batch.

541C

Call the disk read subroutine at 57C8H to read back the track for verification.

541F

JR NZ,5422H 20 01

If read error (NZ), JUMP to 5422H to keep the error code.

5421

XOR A AF

Clear Register A to zero on successful read.

5422

JR Z,5428H 28 04

If read was successful (Z), JUMP to 5428H to compare with original status.

5424

CP 06H FE 06

Compare error code with 06H (Record Not Found). This is expected for unformatted tracks.

5426

JR NZ,5430H 20 08

If NOT Record Not Found (NZ), JUMP to 5430H to handle the error.

5428

CP (HL) BE

Compare the read status with the original write status stored in the track entry.

5429

JR Z,5440H 28 15

If statuses match (Z), JUMP to 5440H to continue verification.

Status mismatch - the track didn't verify correctly. Update granule count and flag error.

542B

CALL 5492H CD 92 54

Call subroutine at 5492H to decrement the remaining granule count (one track failed).

542E

LD A,31H 3E 31

Load Register A with 31H, the error code for "verification failed".

5430

DEC HL 2B

Move HL back to point to the track marker byte.

5431

Call the error handler at 585AH to display the error and ask user to retry or abort.

5434

JR Z,544EH 28 18

If user chose to skip (Z), JUMP to 544EH to finish this batch.

5436

CALL 546DH CD 6D 54

Call subroutine at 546DH to re-write the track and retry the operation.

5439

JR NZ,544EH 20 13

If re-write failed (NZ), JUMP to 544EH to finish this batch.

543B

CALL 5492H CD 92 54

Call subroutine at 5492H to decrement the granule count after the retry.

543E

JR 5406H 18 C6

[LOOP] - Jump back to 5406H to verify the re-written track.

Track verified successfully - compare the sector data with the original to ensure data integrity.

5440

LD B,00H 06 00

Load B with 00H (256 iterations for the comparison loop).

5442

LD DE,(5D10H) ED 5B 10 5D

Load DE with the sector data pointer from 5D10H (where we read the verification data).

5446

INC HL 23

Advance HL to the next byte in the original track data.

5447

LD A,(DE) 1A

Load the byte from the verification buffer (data read back from disk).

5448

CP (HL) BE

Compare with the original data in the track buffer.

5449

INC DE 13

Advance DE to the next byte in the verification buffer.

544A

JR NZ,5461H 20 15

If bytes don't match (NZ), JUMP to 5461H to handle the data mismatch error.

544C

DJNZ 5446H 10 F8

[LOOP] - Decrement B and loop back to 5446H until all 256 bytes are compared.

All 256 bytes verified successfully - advance to the next track entry.

544E

LD HL,0000H 21 00 00

Load HL with 0000H. Note: This is self-modifying code at 544FH - updated with buffer pointer.

5451

INC HL 23

Advance HL past the track marker byte.

5452

INC HL 23

Advance HL past the status byte.

5453

INC H 24

Increment H to advance HL by 256 bytes, moving to the next track entry.

5454

LD (544FH),HL 22 4F 54

Store the updated buffer pointer at 544FH for the next iteration.

5457

Call subroutine at 571BH to update track numbers and advance to the next track position.

545A

LD HL,53ECH 21 EC 53

Load HL with address 53ECH, the write counter location.

545D

DEC (HL) 35

Decrement the write counter (number of tracks remaining to verify).

545E

JR NZ,5406H 20 A6

If tracks remaining (NZ), [LOOP] back to 5406H to verify the next track.

5460

RET C9

All tracks verified - RETURN to caller.

Data mismatch found during verification - handle the compare error.

5461

CALL 5492H CD 92 54

Call subroutine at 5492H to decrement the granule count (verification failed).

5464

LD A,3AH 3E 3A

Load Register A with 3AH, the error code for "compare error" (data mismatch).

5466

Call the error handler at 585AH to display the compare error.

5469

JR Z,544EH 28 E3

If user chose to skip (Z), JUMP to 544EH to continue with the next track.

546B

JR 5406H 18 99

[LOOP] - Jump back to 5406H to retry verification of this track.

546DH - Write Sector to Disk

This subroutine writes a sector (track) from the buffer to the destination disk. It handles error recovery and sets up the proper write command.

546D

PUSH HL E5

Save the current track entry pointer on the stack.

546E

INC HL 23

Advance HL to the status byte of the track entry.

546F

LD A,(HL) 7E

Load the track status byte into Register A.

5470

CP 06H FE 06

Compare with 06H (Record Not Found). Check if this track was originally unformatted.

5472

INC HL 23

Advance HL to the sector data area.

5473

JR NZ,5479H 20 04

If track was formatted (status != 06H), JUMP to 5479H to proceed with write.

Track was unformatted (status 06H) - set a flag to indicate format-only operation.

5475

SET 0,(IX+00H) DD CB 00 C6

Set bit 0 of the drive control byte at IX+00H. This flags the track as needing format, not copy.

5479

CALL 5C8EH CD 8E 5C

Call subroutine at 5C8EH to set up the sector buffer address and size for the write.

547C

LD A,40H 3E 40

Load Register A with 40H, the write sector command flag.

547E

LD (57EBH),A 32 EB 57

Store the write command at 57EBH to set the disk operation to write mode.

5481

CALL 57CEH CD CE 57

Call the disk write subroutine at 57CEH to perform the actual sector write.

5484

RES 0,(IX+00H) DD CB 00 86

Reset bit 0 of the drive control byte to restore normal operation mode.

5488

POP HL E1

Restore the track entry pointer from the stack.

5489

RET Z C8

If write was successful (Z), RETURN to caller.

Write error occurred - call error handler and potentially retry.

548A

Call the error handler at 585AH to display the write error.

548D

JR NZ,546DH 20 DE

If user chose to retry (NZ), [LOOP] back to 546DH to attempt the write again.

548F

OR FFH F6 FF

OR A with FFH to set A to FFH and clear the Z flag. This indicates the write was skipped.

5491

RET C9

RETURN with NZ flag indicating the write was not completed successfully.

5492H - Decrement Granule Count

This small utility subroutine decrements the remaining granule count when a track operation fails or is skipped.

5492

PUSH HL E5

Save the current HL value on the stack.

5493

LD HL,(5B21H) 2A 21 5B

Load HL with the remaining granule count from 5B21H.

5496

DEC HL 2B

Decrement the granule count by one (one track/granule failed).

5497

LD (5B21H),HL 22 21 5B

Store the updated granule count back at 5B21H.

549A

POP HL E1

Restore the original HL value from the stack.

549B

RET C9

RETURN to caller.

549CH - End of Copy/Backup Operation

This code is reached when the end of the source disk is detected during a COPY operation. It writes any remaining buffered tracks to the destination, then finalizes the operation based on mode.

549C

POP HL E1

Remove the track entry pointer from the stack (was pushed at 529DH when error detected end of disk).

549D

CALL 5324H CD 24 53

Call the batch write subroutine at 5324H to write any remaining buffered tracks to the destination disk.

54A0

LD A,(5996H) 3A 96 59

Load the option flags byte 3 from 5996H to check the operation mode.

54A3

BIT 3,A CB 5F

Test bit 3 - the COPY option flag. NZ if COPY mode, Z if BACKUP mode.

54A5

JP NZ,552DH C2 2D 55

If COPY mode (NZ), JUMP to 552DH to display completion message and finish.

54A8

BIT 2,A CB 57

Test bit 2 - the BACKUP option flag. NZ if BACKUP mode, Z if FORMAT mode.

54AA

JR Z,54D4H 28 28

If FORMAT mode (Z), JUMP to 54D4H to continue with format-specific completion.

BACKUP mode completion - copy the directory from source to destination.

54AC

LD A,05H 3E 05

Load Register A with 05H, the operation code for directory copy.

54AE

Call subroutine at 568DH to set up for the directory copy operation.

54B1

CALL 5535H CD 35 55

Call subroutine at 5535H to switch to the destination drive.

54B4

LD HL,(5AF1H) 2A F1 5A

Load HL with the source disk's total granule count from 5AF1H.

54B7

LD (5B23H),HL 22 23 5B

Store this count at 5B23H as the destination's granule count (making them match for BACKUP).

54BA

LD A,(5AEDH) 3A ED 5A

Load the source disk type byte from 5AEDH.

54BD

LD (5B1FH),A 32 1F 5B

Store at 5B1FH as the destination's disk type (copying disk format parameters).

54C0

LD DE,5B17H 11 17 5B

Load DE with 5B17H, the address of the destination drive control block.

54C3

CALL 4428H CD 28 44

Call the DOS file close routine at 4428H to finalize the destination file.

54C6

LD HL,4317H 21 17 43

Load HL with 4317H, the address of the DOS error status byte.

54C9

LD (HL),05H 36 05

Store 05H as the operation code in the status byte.

54CB

If file close failed (NZ), JUMP to the error handler at 521AH.

54CE

LD HL,402DH 21 2D 40

Load HL with 402DH, the address of a completion message or return point.

54D1

JP 5222H C3 22 52

JUMP to 5222H to complete the operation and return to DOS.

54D4

JP 501CH C3 1C 50

JUMP to 501CH to continue with FORMAT-specific completion (directory initialization).

54D7H - Drive Parameter Check Utility

This utility subroutine checks drive parameters for double-sided disk handling and side selection.

54D7

LD D,(IX+04H) DD 56 04

Load Register D with the track number from the drive control block at IX+04H.

54DA

LD C,(IX+06H) DD 4E 06

Load Register C with the side/sector value from IX+06H.

54DD

LD A,(IX+02H) DD 7E 02

Load Register A with the drive configuration byte from IX+02H.

54E0

AND 1CH E6 1C

Mask with 1CH to isolate bits 2-4 (disk type/density bits).

54E2

CP 08H FE 08

Compare with 08H to check if this is a double-sided disk configuration.

54E4

RET NZ C0

If NOT double-sided (NZ), RETURN - no side selection needed.

Double-sided disk - toggle the side selection bit.

54E5

LD A,C 79

Load the side/sector value into Register A.

54E6

XOR 20H EE 20

XOR with 20H to toggle bit 5 (the side selection bit).

54E8

LD (IX+06H),A DD 77 06

Store the updated side/sector value back at IX+06H.

54EB

RET C9

RETURN to caller with side selection updated.

54ECH - Store Sector and Track Parameters

This utility stores sector and track values into the drive control block.

54EC

LD (IX+06H),C DD 71 06

Store Register C as the sector number at IX+06H in the drive control block.

54EF

LD (IX+07H),E DD 73 07

Store Register E as the track number at IX+07H in the drive control block.

54F2

RET C9

RETURN to caller.

54F3H - Copy Drive Parameters from Work Area

This subroutine copies drive configuration parameters from the appropriate work area based on the option flags.

54F3

LD A,C 79

Load Register A with the value from Register C (the option flags).

54F4

AND 0CH E6 0C

Mask with 0CH to isolate bits 2-3 (COPY/BACKUP flags).

54F6

LD BC,0010H 01 00 10

Load BC with 0010H (16), the number of bytes to copy for the drive control block.

54F9

LD DE,42D0H 11 D0 42

Load DE with 42D0H, the destination address in the DOS work area.

54FC

LD HL,5983H 21 83 59

Load HL with 5983H, the source address for COPY/BACKUP mode parameters.

54FF

JR NZ,5508H 20 07

If COPY or BACKUP mode (NZ), JUMP to 5508H to perform the copy.

FORMAT mode - use different source parameters.

5501

LD HL,598BH 21 8B 59

Load HL with 598BH, the source address for FORMAT mode parameters.

5504

LD E,D8H 1E D8

Load E with D8H, changing destination to 42D8H for FORMAT mode.

5506

LD C,08H 0E 08

Load C with 08H (8 bytes), the reduced size for FORMAT mode copy.

5508

LDIR ED B0

Block copy BC bytes from (HL) to (DE). Copy the drive parameters to the work area.

550A

LD HL,(59D1H) 2A D1 59

Load HL with the high memory limit from 59D1H.

550D

LD DE,(59C3H) ED 5B C3 59

Load DE with the program end address from 59C3H.

5511

OR A B7

Clear the Carry flag for subtraction.

5512

SBC HL,DE ED 52

Calculate HL = high memory - program end (available memory).

5514

EX DE,HL EB

Exchange DE and HL. Now DE = available memory, HL = program end.

5515

JR C,5528H 38 11

If borrow (no available memory), JUMP to 5528H to skip memory allocation.

5517

JR Z,5528H 28 0F

If exactly zero available (Z), JUMP to 5528H to skip.

Memory is available - set up the hash table or directory buffer.

5519

LD HL,(59C3H) 2A C3 59

Load HL with the program end address from 59C3H.

551C

LD A,(59BCH) 3A BC 59

Load Register A with a configuration byte from 59BCH.

551F

Call the DOS memory allocation routine at 4CB4H to set up the buffer.

5522

LD H,42H 26 42

Load H with 42H, setting up the high byte of the work area address.

5524

LD C,A 4F

Copy the returned value from the allocation to Register C.

5525

CALL 5762H CD 62 57

Call subroutine at 5762H to complete the buffer setup.

5528

CALL 491FH CD 1F 49

Call the DOS directory access routine at 491FH to initialize directory handling.

552B

JR NZ,54CBH 20 9E

If directory access failed (NZ), JUMP to 54CBH to handle the error.

552D

LD HL,5A1FH 21 1F 5A

Load HL with 5A1FH, the address of the operation complete message.

5530

Call the DOS print message routine at 4467H to display the completion message.

5533

JR 54CEH 18 99

JUMP to 54CEH to finish the operation and return to DOS.

5535H - Set Up Destination Drive

This subroutine configures the system to use the destination drive for write operations.

5535

LD HL,5956H 21 56 59

Load HL with 5956H, the address of the destination drive number storage.

5538

CALL 5585H CD 85 55

Call subroutine at 5585H to set up drive-specific parameters from (HL).

553B

INC HL 23

Advance HL past the drive number.

553C

INC HL 23

Advance to the drive control block pointer location.

553D

LD E,(HL) 5E

Load the low byte of the drive control block address into E.

553E

INC HL 23

Advance to the high byte.

553F

LD D,(HL) 56

Load the high byte of the control block address into D.

5540

PUSH DE D5

Push the control block address onto the stack.

5541

POP IX DD E1

Pop the control block address into IX for indexed addressing.

5543

LD A,(DE) 1A

Load the first byte of the control block (drive status) into A.

5544

BIT 7,A CB 7F

Test bit 7 - the drive ready/initialized flag. NZ if drive is ready.

5546

RET NZ C0

If drive already initialized (NZ), RETURN - no further setup needed.

Drive not initialized - perform drive selection and initialization.

5547

LD B,00H 06 00

Load B with 00H, parameter for drive access routine.

5549

LD A,17H 3E 17

Load Register A with 17H, the offset for secondary drive control block.

554B

CP E BB

Compare with E (low byte of control block address). Check if this is the destination drive block.

554C

JR Z,5556H 28 08

If destination drive block (Z), JUMP to 5556H to use secondary access routine.

554E

CALL 4424H CD 24 44

Call the primary drive access routine at 4424H.

5551

JR Z,5570H 28 1D

If successful (Z), JUMP to 5570H to store the sector number.

5553

If failed (NZ), JUMP to the error handler at 521AH.

5556

CALL 4420H CD 20 44

Call the secondary drive access routine at 4420H.

5559

JR NZ,5553H 20 F8

If failed (NZ), JUMP to 5553H to handle the error.

Drive access successful - verify source and destination match for COPY operation.

555B

LD DE,(5AEBH) ED 5B EB 5A

Load DE with the source disk identifier from 5AEBH.

555F

LD HL,(5B1DH) 2A 1D 5B

Load HL with the destination disk identifier from 5B1DH.

5562

RST 18H DF

Call the compare HL,DE routine via RST 18H. Z if disks match.

5563

JR NZ,5570H 20 0B

If disks don't match (NZ), JUMP to 5570H - this is expected for COPY to different disk.

Source and destination match - display warning about copying to same disk.

5565

LD HL,5A24H 21 24 5A

Load HL with 5A24H, the address of a warning message about same disk.

5568

LD A,(5940H) 3A 40 59

Load the operation status byte from 5940H.

556B

CP 06H FE 06

Compare with 06H (threshold for warning display).

556D

JP C,5243H DA 43 52

If below threshold (Carry), JUMP to 5243H to display the warning.

5570

LD HL,(593EH) 2A 3E 59

Load HL with the sector storage address from 593EH.

5573

LD A,(IX+06H) DD 7E 06

Load the current sector number from the drive control block at IX+06H.

5576

LD (HL),A 77

Store the sector number at the address in HL.

5577

RET C9

RETURN to caller with drive set up.

5578H - Drive Setup Entry Points

These are multiple entry points for the drive setup routine, each loading a different drive parameter address into HL before falling through to the common setup code at 5585H.

5578

LD HL,594CH 21 4C 59

Load HL with 594CH, the address of the source drive parameters.

557B

JR 5585H 18 08

JUMP to 5585H to continue with the common setup code.

557D

LD HL,5956H 21 56 59

Load HL with 5956H, the address of the destination drive parameters.

5580

JR 5585H 18 03

JUMP to 5585H to continue with the common setup code.

5582

LD HL,5942H 21 42 59

Load HL with 5942H, the address of the primary operation drive parameters.

5585

LD (593EH),HL 22 3E 59

Store the parameter address at 593EH as the current drive parameter pointer.

5588

LD A,FFH 3E FF

Load Register A with FFH to set a flag value.

558A

LD (4930H),A 32 30 49

Store FFH at 4930H in the DOS work area, marking drive parameters as updated.

558D

LD A,(HL) 7E

Load the first byte of the drive parameters (drive number) into A.

558E

INC A 3C

Increment A. If drive was FFH (uninitialized), A becomes 00H and Z flag is set.

558F

RET Z C8

If drive uninitialized (Z), RETURN immediately - no setup needed.

Drive is initialized - save registers and check for disk change.

5590

PUSH HL E5

Save the drive parameter pointer on the stack.

5591

PUSH DE D5

Save DE on the stack.

5592

PUSH BC C5

Save BC on the stack.

5593

LD A,(593BH) 3A 3B 59

Load the operation mode flags from 593BH.

5596

BIT 7,A CB 7F

Test bit 7 - the multi-disk operation flag. NZ if multi-disk mode active.

5598

LD B,00H 06 00

Load B with 00H, the default flag value for single-disk mode.

559A

CALL NZ,5658H C4 58 56

If multi-disk mode (NZ), CALL 5658H to handle disk change detection.

559D

LD C,(HL) 4E

Load the drive number from the parameter block into C.

559E

INC HL 23

Advance to the next byte in the parameter block.

559F

LD B,(HL) 46

Load the drive status flags into B.

55A0

LD DE,0007H 11 07 00

Load DE with 0007H, the offset to the drive control block pointer.

55A3

ADD HL,DE 19

Add offset to HL to point to the control block address location.

55A4

LD E,(HL) 5E

Load the low byte of the drive control block address into E.

55A5

INC HL 23

Advance to the high byte.

55A6

LD D,(HL) 56

Load the high byte of the control block address into D.

55A7

LD HL,5940H 21 40 59

Load HL with 5940H, the address of the operation status bytes.

55AA

LD A,(HL) 7E

Load the first status byte into A.

55AB

AND B A0

AND with the drive status flags. Tests if status matches expected pattern.

55AC

LD A,(HL) 7E

Load the first status byte again (reload for next operation).

55AD

INC HL 23

Advance to the second status byte at 5941H.

55AE

JR Z,55B5H 28 05

If status check passed (Z), JUMP to 55B5H to continue with drive access.

Status mismatch - update the second status byte to reflect current state.

55B0

XOR B A8

XOR with the drive status flags to find different bits.

55B1

XOR FFH EE FF

Invert all bits to create a mask of matching bits.

55B3

AND (HL) A6

AND with the second status byte to preserve only matching bits.

55B4

LD (HL),A 77

Store the updated status byte.

55B5

LD A,C 79

Load the drive number into Register A.

55B6

CALL 4776H CD 76 47

Call the DOS drive select routine at 4776H to activate the drive.

55B9

If drive select failed (NZ), JUMP to the error handler at 521AH.

55BC

PUSH HL E5

Save the status pointer on the stack.

55BD

LD A,(HL) 7E

Load the current status byte.

55BE

AND B A0

AND with drive flags to test if disk is present.

55BF

JR NZ,55ECH 20 2B

If disk present (NZ), JUMP to 55ECH to proceed with disk access.

No disk present - prompt user to insert disk.

55C1

LD HL,59EEH 21 EE 59

Load HL with 59EEH, the address of the "Insert disk" prompt message.

55C4

Call the DOS print message routine at 4467H to display the insert disk prompt.

55C7

LD H,D 62

Copy high byte of control block address to H.

55C8

LD L,E 6B

Copy low byte of control block address to L. HL now points to control block.

55C9

Call 4467H again to display the disk name from the control block.

55CC

LD A,C 79

Load the drive number into A.

55CD

ADD 30H C6 30

Add 30H to convert to ASCII digit ('0'=30H, '1'=31H, etc.).

55CF

LD (5A1DH),A 32 1D 5A

Store the ASCII drive number in the message template at 5A1DH.

55D2

LD HL,5A02H 21 02 5A

Load HL with 5A02H, the address of the "in drive N" message template.

55D5

Call 4467H to display the complete "in drive N" message.

Wait for user to press ENTER after inserting the disk.

55D8

PUSH BC C5

Save BC on the stack.

55D9

LD BC,8000H 01 00 80

Load BC with 8000H, a parameter for the key wait routine.

55DC

PUSH DE D5

Save DE on the stack.

55DD

CALL 4CEDH CD ED 4C

Call the DOS keyboard input routine at 4CEDH to wait for a keypress.

55E0

POP DE D1

Restore DE from the stack.

55E1

POP BC C1

Restore BC from the stack.

55E2

CALL 572BH CD 2B 57

Call subroutine at 572BH to check for BREAK key.

55E5

CP 0DH FE 0D

Compare with 0DH (ENTER key). Z if ENTER was pressed.

55E7

JR NZ,55E2H 20 F9

If not ENTER (NZ), [LOOP] back to 55E2H to keep waiting.

55E9

Call subroutine at 5881H to clear the prompt message from the screen.

55EC

LD A,C 79

Load the drive number into A.

55ED

CALL 47ECH CD EC 47

Call the DOS disk verify routine at 47ECH to check the disk is readable.

55F0

JR NZ,55C1H 20 CF

If disk not ready (NZ), [LOOP] back to 55C1H to prompt again.

55F2

POP HL E1

Restore the status pointer from the stack.

55F3

LD A,(HL) 7E

Load the current status byte.

55F4

OR B B0

OR with the drive flags to mark disk as present.

55F5

LD (HL),A 77

Store the updated status byte.

55F6

LD HL,5B57H 21 57 5B

Load HL with 5B57H, the address of the disk parameter list.

55F9

JR 563BH 18 40

JUMP to 563BH to continue with disk parameter processing.

55FBH - Disk Parameter Processing Loop

This code processes disk parameters, handling different disk types and swapping buffers as needed for multi-disk operations.

55FB

PUSH HL E5

Save the current parameter list pointer on the stack.

55FC

JR Z,560DH 28 0F

If Z flag set (from previous test), JUMP to 560DH to skip error check.

55FE

LD A,(4317H) 3A 17 43

Load the DOS error code from 4317H.

5601

CP C B9

Compare with the current drive number in C.

5602

JR Z,560DH 28 09

If error matches this drive (Z), JUMP to 560DH to handle it.

5604

BIT 5,(HL) CB 6E

Test bit 5 of the current parameter byte - the "skip on error" flag.

5606

JR Z,5637H 28 2F

If skip flag not set (Z), JUMP to 5637H to continue normally.

5608

LD A,33H 3E 33

Load Register A with 33H, the error code for "wrong disk in drive".

560A

JUMP to the error handler at 521AH to report the error.

560D

LD A,(430CH) 3A 0C 43

Load the DOS configuration byte from 430CH.

5610

XOR (HL) AE

XOR with the current parameter byte to find differences.

5611

AND 20HAND 00100000 E6 20

Mask with 20H to test only bit 5 (buffer swap needed).

5613

JR Z,5637H 28 22

If bit 5 matches (Z), JUMP to 5637H - no buffer swap needed.

Buffer swap needed - exchange buffer contents between source and destination.

5615

XOR (HL) AE

XOR again to restore original bits and toggle bit 5.

5616

LD (HL),A 77

Store the updated parameter byte with bit 5 toggled.

5617

INC HL 23

Advance to the buffer pointer location.

5618

LD A,(HL) 7E

Load the low byte of the buffer address.

5619

INC HL 23

Advance to the high byte.

561A

LD H,(HL) 66

Load the high byte of the buffer address into H.

561B

LD L,A 6F

Load the low byte into L. HL now points to the buffer.

561C

JR 562FH 18 11

JUMP to 562FH to continue with the buffer swap.

[LOOP] - Buffer swap loop: exchange bytes between two buffers.

561E

LD A,(HL) 7E

Load the byte count from the current position.

561F

OR A B7

Test if byte count is zero. Z flag set if done.

5620

LD B,A 47

Copy byte count to B for the swap loop.

5621

INC HL 23

Advance past the byte count.

5622

EX DE,HL EB

Exchange DE and HL for the swap operation.

5623

JR Z,562FH 28 0A

If byte count zero (Z), JUMP to 562FH to check for next block.

5625

EX DE,HL EB

Exchange back for the swap.

5626

LD C,(HL) 4E

Load byte from first buffer into C.

5627

LD A,(DE) 1A

Load byte from second buffer into A.

5628

LD (HL),A 77

Store second buffer byte into first buffer.

5629

LD A,C 79

Get first buffer byte from C.

562A

LD (DE),A 12

Store first buffer byte into second buffer. Swap complete for this byte.

562B

INC HL 23

Advance first buffer pointer.

562C

INC DE 13

Advance second buffer pointer.

562D

DJNZ 5626H 10 F7

[LOOP] - Decrement B and loop back to 5626H until all bytes swapped.

562F

LD E,(HL) 5E

Load low byte of next block pointer.

5630

INC HL 23

Advance to high byte.

5631

LD D,(HL) 56

Load high byte of next block pointer.

5632

INC HL 23

Advance past the pointer.

5633

LD A,D 7A

Load high byte into A.

5634

OR E B3

OR with low byte. Z if pointer is 0000H (end of list).

5635

JR NZ,561EH 20 E7

If more blocks (NZ), [LOOP] back to 561EH to process next block.

5637

POP HL E1

Restore the parameter list pointer from the stack.

5638

INC HL 23

Advance to next parameter entry.

5639

INC HL 23

Advance past the entry.

563A

INC HL 23

Advance to the entry type byte.

563B

LD A,(HL) 7E

Load the entry type byte.

563C

CP 02H FE 02

Compare with 02H. Entries with type >= 02H need processing.

563E

LD C,A 4F

Copy entry type to C for later use.

563F

INC HL 23

Advance to the next entry.

5640

JR NC,55FBH 30 B9

If type >= 02H (No Carry), [LOOP] back to 55FBH to process this entry.

Entry type < 02H - done processing, restore registers and return.

5642

POP BC C1

Restore BC from the stack.

5643

POP DE D1

Restore DE from the stack.

5644

POP HL E1

Restore the original drive parameter pointer from the stack.

5645

RET C9

RETURN to caller with drive set up.

5646H - Flush All Drive Buffers

This subroutine iterates through all three drive parameter blocks (at 5942H, 594CH, and 5956H) and flushes any pending buffer data for drives that are currently active. It is called from the error handler at 5230H before exiting to ensure no data is lost. Register B on entry contains a retry count (typically 5).

5646

LD HL,5942H 21 42 59

Load Register HL with the address of the drive parameter block table (5942H). This table contains status information for up to 3 drives, with each entry being 10 (0AH) bytes.

5649

LD C,03H 0E 03

Load Register C with 3, the number of drive entries to process. This serves as a loop counter for iterating through all possible drives (drives 0, 1, and 2).

[LOOP START] - Begin iterating through each drive parameter block.

564B

LD A,(HL) 7E

Load Register A with the drive status byte from the current drive parameter block. A value of FFH indicates the drive slot is unused/inactive.

564C

INC A 3C

Increment Register A. This is a clever test: if the drive status was FFH (inactive/unused), incrementing it produces 00H and sets the Z FLAG. Any other value means the drive is active.

564D

CALL NZ,5658H C4 58 56

If the NZ FLAG is set (meaning the drive is active - status was not FFH), CALL the buffer flush subroutine at 5658H to write any pending data to disk for this drive.

5650

LD DE,000AH 11 0A 00

Load Register DE with 10 (0AH), the size of each drive parameter block entry in bytes.

5653

ADD HL,DE 19

Add DE to HL, advancing the pointer to the next drive parameter block (from 5942H to 594CH to 5956H).

5654

DEC C 0D

Decrement the drive counter in Register C.

5655

JR NZ,564BH 20 F4

If the NZ FLAG is set (more drives to check), JUMP back to 564BH to process the next drive. [LOOP]

5657

RET C9

Return to the caller. All drive buffers have been flushed.

5658H - Flush Single Drive Buffer

This subroutine flushes the buffer for a single drive. On entry, HL points to the drive parameter block and A contains the drive status byte. Register B (from the caller) contains a retry/error handling flag. This routine interfaces with the DOS buffer management system to write any dirty sectors back to disk.

5658

LD A,(HL) 7E

Load Register A with the drive number from the first byte of the drive parameter block pointed to by HL.

5659

PUSH HL E5

Save the drive parameter block pointer onto the stack for later restoration.

565A

PUSH DE D5

Save Register DE onto the stack.

565B

CALL 4776H CD 76 47

CALL the SYS0 buffer lookup routine at 4776H. This routine searches for a buffer associated with the drive number in A. Returns with HL pointing to the buffer control block, and B containing buffer flags. Z FLAG set if no buffer found.

565E

JR NZ,5684H 20 24

If the NZ FLAG is set (buffer found), JUMP to 5684H to check for errors. This is taken if the buffer lookup succeeded.

Buffer was found. Now determine whether it's a read buffer or write buffer by checking bit 0 of the flags in B, and copy the appropriate data.

5660

LD DE,0004H 11 04 00

Load Register DE with 4, the offset to the read buffer pointer within the buffer control block.

5663

BIT 0,B CB 40

Test bit 0 of Register B (buffer flags). If set, this is a write buffer; if clear, it's a read buffer.

5665

JR Z,5669H 28 02

If the Z FLAG is set (bit 0 clear, read buffer), JUMP to 5669H to skip the offset adjustment.

5667

INC DE 13

Increment DE to 5 (write buffer offset is 2 bytes higher).

5668

INC DE 13

Increment DE to 6. For write buffers, the pointer is at offset 6 instead of 4.

5669

ADD HL,DE 19

Add the offset in DE to HL, pointing to the buffer address pointer within the control block.

566A

LD E,(HL) 5E

Load the low byte of the buffer address into Register E.

566B

INC HL 23

Increment HL to point to the high byte.

566C

LD D,(HL) 56

Load the high byte of the buffer address into Register D. DE now contains the buffer address.

566D

LD HL,(4399H) 2A 99 43

Load Register HL with the contents of system buffer pointer at 4399H (SYS0 data area). This is the destination/source for the copy operation.

5670

BIT 1,B CB 48

Test bit 1 of Register B (buffer flags). This determines the direction of the copy.

5672

JR NZ,5675H 20 01

If the NZ FLAG is set (bit 1 set), JUMP to 5675H keeping HL as source. Otherwise swap source/destination.

5674

EX DE,HL EB

Exchange DE and HL, swapping the source and destination addresses for the copy.

5675

PUSH BC C5

Save the buffer flags (B) and any counter value (C) onto the stack.

5676

LD BC,000AH 01 0A 00

Load Register BC with 10, the number of bytes to copy. This copies the drive parameter/status information.

5679

LDIR ED B0

Block copy 10 bytes from the source (HL) to the destination (DE). This synchronizes the buffer data with the drive parameters.

567B

POP BC C1

Restore the buffer flags and counter from the stack.

567C

CALL the SYS0 buffer release routine at 4773H to mark the buffer as flushed/released.

567F

JR NZ,5684H 20 03

If the NZ FLAG is set (error occurred during release), JUMP to 5684H to handle the error.

[SUCCESS PATH] - Buffer flush completed successfully.

5681

POP DE D1

Restore Register DE from the stack.

5682

POP HL E1

Restore the drive parameter block pointer from the stack.

5683

RET C9

Return to the caller with Z FLAG set (success).

[ERROR PATH] - Check if errors should be suppressed or reported.

5684

BIT 2,B CB 50

Test bit 2 of Register B. If set, this indicates errors should be suppressed (silent mode).

5686

JR NZ,5681H 20 F9

If the NZ FLAG is set (suppress errors), JUMP to 5681H to restore registers and return without error.

5688

JUMP to the main error handler at 521AH to report the disk error to the user.

568BH - Initialize Primary Drive with Retry

This subroutine initializes the primary (system) drive with error code 04H and sets up for operation with error retry enabled.

568B

LD A,04H 3E 04

Load Register A with error code 04H (disk not ready or initialization error).

568D

LD C,FFH 0E FF

Load Register C with FFH, indicating "use default drive" or "all drives" mode.

568F

PUSH AF F5

Save the error code and flags onto the stack.

5690

CALL 5582H CD 82 55

CALL the primary drive setup routine at 5582H to initialize the drive specified in C.

5693

POP AF F1

Restore the error code and flags from the stack.

5694

OR A B7

Test Register A by ORing it with itself. This sets flags based on the error code.

5695

RET Z C8

If the Z FLAG is set (A=0, no error), RETURN immediately.

5696

OR E0H F6 E0

OR Register A with E0H, setting the upper bits to indicate a specific error type. This converts the error code to a DOS error format.

5698

RST 28H EF

Execute RST 28H, the DOS error signaling routine. This sets up the error condition for the system.

5699

INC HL 23

Increment HL (part of multi-byte operation following RST 28H or entry point for 56A2H).

569A

INC HL 23

Increment HL again.

569B

INC HL 23

Increment HL a third time, advancing past a 3-byte structure.

569C

LD DE,(5D14H) ED 5B 14 5D

Load Register DE with the current buffer pointer from 5D14H.

56A0

RST 18H DF

Execute RST 18H, the DOS compare/dispatch routine.

56A1

RET C9

Return to the caller.

56A2H - Verify End-of-Disk Condition (COPY Mode)

This subroutine checks for the end-of-disk condition during COPY operations. It loops until bit 5 of a status byte is set, indicating the disk operation is complete.

56A2

CALL the subroutine at 5699H to advance the pointer and load the current buffer position.

56A5

RET Z C8

If the Z FLAG is set (operation complete), RETURN to the caller.

56A6

BIT 5,(HL) CB 6E

Test bit 5 of the byte pointed to by HL. This is the end-of-disk flag in the status byte.

56A8

JR Z,56A2H 28 F8

If the Z FLAG is set (bit 5 clear, not at end of disk), JUMP back to 56A2H to continue checking. [LOOP]

End-of-disk detected. Save the current position and set up for the next operation.

56AA

LD (52BAH),HL 22 BA 52

Store HL (current position pointer) at 52BAH for later reference.

56AD

INC HL 23

Increment HL to point to the next byte in the structure.

56AE

LD C,(HL) 4E

Load Register C with the sector count or parameter from the next byte.

56AF

INC HL 23

Increment HL again.

56B0

LD A,(HL) 7E

Load Register A with the next byte (track or head number).

56B1

LD (52D2H),A 32 D2 52

Store this value at 52D2H (track/head storage location).

56B4

LD IX,5AE5H DD 21 E5 5A

Load Index Register IX with 5AE5H, the address of the filename/FCB buffer.

56B8

LD A,C 79

Copy the sector count from Register C to Register A.

56B9

LD (4F56H),A 32 56 4F

Store the sector count at 4F56H (sector counter in the disk I/O area).

56BC

CALL 56F4H CD F4 56

CALL the disk seek routine at 56F4H to position the head at the required track.

56BF

XOR A AF

Clear Register A to zero.

56C0

LD (4F5EH),A 32 5E 4F

Store zero at 4F5EH (clearing a status or counter byte).

56C3

INC HL 23

Increment HL to point to the next parameter.

56C4

CALL 4E21H CD 21 4E

CALL the subroutine at 4E21H (parameter setup routine).

56C7

EX DE,HL EB

Exchange DE and HL, moving the calculated address to HL.

56C8

LD A,E 7B

Load Register A with the low byte of the address (now in E after exchange).

56C9

ADD 10H C6 10

Add 16 (10H) to Register A, calculating an offset.

56CB

LD E,A 5F

Store the result back in Register E.

56CC

CALL 4F2EH CD 2E 4F

CALL the subroutine at 4F2EH (disk I/O execution).

56CF

JR NZ,56FEH 20 2D

If the NZ FLAG is set (error occurred), JUMP to 56FEH to handle the error.

56D1

OR FFH F6 FF

OR Register A with FFH, setting A to FFH and clearing the Z FLAG.

56D3

RET C9

Return with NZ FLAG set (A=FFH indicates success with end-of-disk reached).

56D4H - Calculate Sector Address

This subroutine calculates the absolute sector address from a logical sector number. It uses the disk geometry parameters from the IY register base.

56D4

LD L,A 6F

Load the low byte of HL with Register A (the logical sector number).

56D5

LD H,00H 26 00

Clear the high byte of HL, making HL = the sector number as a 16-bit value.

56D7

LD A,(IY+8EH) FD 7E 8E

Load Register A with the byte at IY+8EH (offset 142 from IY base 4380H = 440EH). This contains disk geometry information.

56DA

JP 4C94H C3 94 4C

JUMP to the SYS0 sector calculation routine at 4C94H to complete the address computation.

56DDH - Get Directory Entry Address

This subroutine retrieves the address of a directory entry. It calls the SYS0 directory lookup routine.

56DD

CALL 494BH CD 4B 49

CALL the SYS0 directory entry lookup routine at 494BH. This routine locates the directory entry for the current file.

56E0

JR 56FDH 18 1B

JUMP to 56FDH to check the result and handle any errors.

56E2H - Seek to Specified Sector

This subroutine seeks to a specified sector, handling track changes as needed. On entry, A contains the target sector number.

56E2

PUSH AF F5

Save Register A (target sector) and flags onto the stack.

56E3

AND 1FHAND 00011111 E6 1F

Mask Register A with 1FH (00011111 binary), extracting the sector number within the track (0-31).

56E5

INC A 3C

Increment to convert from 0-based to 1-based sector numbering.

56E6

INC A 3C

Increment again (sectors are numbered starting at 2, not 0 or 1).

56E7

LD HL,570EH 21 0E 57

Load HL with address 570EH, which contains the current sector number.

56EA

CP (HL) BE

Compare Register A with the current sector number at (HL). Sets Z FLAG if they match.

56EB

CALL NZ,570DH C4 0D 57

If the NZ FLAG is set (different sector), CALL 570DH to update the sector counter.

56EE

POP AF F1

Restore the original sector value and flags from the stack.

56EF

CALL 492FH CD 2F 49

CALL the SYS0 seek routine at 492FH to position the disk head.

56F2

JR 56FDH 18 09

JUMP to 56FDH to check the result.

56F4H - Seek to Track

This is a simpler seek routine that positions the head to a track without sector positioning.

56F4

CALL 4936H CD 36 49

CALL the SYS0 track seek routine at 4936H.

56F7

JR 56FDH 18 04

JUMP to 56FDH to check the result.

56F9H - Home Drive Head

This routine homes the drive head (seeks to track 0).

56F9

XOR A AF

Clear Register A to zero (track 0).

56FA

CALL 490AH CD 0A 49

CALL the SYS0 seek-to-track routine at 490AH with track 0 in A.

56FD

RET Z C8

If the Z FLAG is set (operation successful), RETURN to the caller.

56FE

JUMP to the main error handler at 521AH if an error occurred.

5701H - Read Disk Sector

This subroutine reads a sector from the disk.

5701

CALL 4922H CD 22 49

CALL the SYS0 read sector routine at 4922H.

5704

JR 56FDH 18 F7

JUMP to 56FDH to check the result and handle any errors.

5706H - Initialize Sector Counter

This routine initializes the sector counter from the system value.

5706

LD A,(4930H) 3A 30 49

Load Register A with the default sector count from 4930H (SYS0 area).

5709

LD (570EH),A 32 0E 57

Store this value at 570EH as the current sector counter.

570C

RET C9

Return to the caller.

570DH - Update Sector Counter

This subroutine updates the sector counter, potentially triggering a track seek if necessary.

570D

LD A,FFH 3E FF

Load Register A with FFH (-1 or 255).

570E

DATA 3C

Self-modifying code location: This byte (3CH = INC A) is modified at runtime to store the current sector number. When executed, it increments A.

570F

INC A 3C

Increment Register A again.

5710

RET Z C8

If the Z FLAG is set (A wrapped to 0), RETURN - no track change needed.

5711

LD A,FFH 3E FF

Load Register A with FFH to reset the sector counter.

5713

LD (570EH),A 32 0E 57

Store FFH at the sector counter location (570EH).

5716

CALL 491FH CD 1F 49

CALL the SYS0 step-in routine at 491FH to move to the next track.

5719

JR 56FDH 18 E2

JUMP to 56FDH to check the result.

571BH - Toggle Track Progress Indicator

This subroutine toggles an asterisk (*) character on the screen to indicate track processing progress. It displays at position 3C3FH (top-right corner of the video display, column 63 of row 0).

571B

LD A,(3C3FH) 3A 3F 3C

Load Register A with the character currently displayed at screen position 3C3FH (video RAM, top-right area).

571E

CP 2AH FE 2A

Compare Register A with 2AH (ASCII code for * asterisk). Sets Z FLAG if currently showing asterisk.

5720

LD A,2AH 3E 2A

Load Register A with 2AH (asterisk character), preparing to display it.

5722

JR NZ,5726H 20 02

If the NZ FLAG is set (not currently showing asterisk), JUMP to 5726H to display the asterisk.

5724

LD A,20H 3E 20

Load Register A with 20H (ASCII space). If asterisk was already showing, we'll display a space to toggle it off.

5726

LD (3C3FH),A 32 3F 3C

Store Register A at screen position 3C3FH, toggling the progress indicator between asterisk and space.

5729

JR 5733H 18 08

JUMP to 5733H to continue with the BREAK key check.

572BH - Check for BREAK Key with Delay

This subroutine checks for the BREAK key while providing a small delay. It allows the user to cancel long-running operations like FORMAT or COPY. Returns the key code in A.

572B

PUSH DE D5

Save Register DE onto the stack.

572C

CALL 002BH CD 2B 00

CALL the ROM keyboard scan routine at 002BH. This routine scans the keyboard and returns any pressed key in A.

572F

CALL 45B5H CD B5 45

CALL the SYS0 key processing routine at 45B5H to handle special key combinations.

5732

POP DE D1

Restore Register DE from the stack.

Fall through to check for BREAK key and special conditions.

5733

PUSH AF F5

Save the key code and flags onto the stack.

5734

LD A,(5995H) 3A 95 59

Load Register A with the option flags from 5995H. Bit 7 indicates "no user interaction" mode.

5737

BIT 7,A CB 7F

Test bit 7 of the option flags. If set, BREAK checking is disabled.

5739

JR NZ,574FH 20 14

If the NZ FLAG is set (no-interaction mode), JUMP to 574FH to skip BREAK check.

Check if BREAK+UP or BREAK+DOWN is pressed (keyboard row 3840H).

573B

LD A,(3840H) 3A 40 38

Load Register A from keyboard memory 3840H (row 6: ENTER, CLEAR, BREAK, UP, DOWN, LEFT, RIGHT, SPACE).

573E

AND 48HAND 01001000 E6 48

Mask with 48H (01001000 binary), isolating bits 3 (UP arrow) and 6 (BREAK key).

5740

JR Z,574FH 28 0D

If the Z FLAG is set (neither BREAK+UP nor BREAK+DOWN pressed), JUMP to 574FH to exit normally.

[BREAK DETECTED] - Wait for key release and check for retry/cancel.

5742

LD A,(3840H) 3A 40 38

Load Register A from keyboard row 3840H again.

5745

AND 09H E6 09

Mask with 09H (00001001 binary), isolating bits 0 (ENTER) and 3 (UP).

5747

JR Z,5742H 28 F9

If the Z FLAG is set (waiting for ENTER or UP release), LOOP back to 5742H. [WAIT LOOP]

5749

RRCA 0F

Rotate Register A right through carry. This moves bit 0 (ENTER status) into the Carry flag.

574A

LD A,39H 3E 39

Load Register A with error code 39H ("Operator Break" error).

574C

JP NC,521AH D2 1A 52

If the NC FLAG is set (Carry clear, ENTER was pressed = cancel), JUMP to error handler at 521AH with the break error.

574F

POP AF F1

Restore the original key code and flags from the stack.

5750

RET C9

Return to the caller with the key code in A.

5751H - Check Free Space and Allocate Sectors

This subroutine manages sector allocation for the disk bitmap. It checks if there's room for more sectors and handles bitmap manipulation. Called during FORMAT and COPY operations to track used/free sectors.

5751

LD A,L 7D

Load Register A with the low byte of HL (current bitmap position).

5752

CP 60H FE 60

Compare Register A with 60H (96 decimal). Check if we've reached the end of the bitmap area.

5754

POP BC C1

Restore Register BC from the stack.

5755

POP DE D1

Restore Register DE from the stack.

5756

POP HL E1

Restore Register HL from the stack.

5757

RET NC D0

If the NC FLAG is set (position >= 60H, at end), RETURN to caller - no more space.

5758

LD A,(59C6H) 3A C6 59

Load Register A with the maximum track number from 59C6H.

575B

CP 61H FE 61

Compare with 61H (97 decimal) to check disk capacity limit.

575D

RET NC D0

If the NC FLAG is set (max track >= 97, exceeds limit), RETURN.

575E

LD A,L 7D

Load Register A with the low byte of HL again.

575F

ADD 60H C6 60

Add 60H to Register A, calculating the absolute bitmap position.

5761

LD L,A 6F

Store the result back in Register L.

5762

PUSH HL E5

Save the updated bitmap pointer onto the stack.

5763

PUSH DE D5

Save Register DE onto the stack.

5764

PUSH BC C5

Save Register BC onto the stack.

[SECTOR ALLOCATION LOOP] - Process the bitmap to mark sectors.

5765

LD A,L 7D

Load Register A with the current bitmap byte position.

5766

CP C0H FE C0

Compare with C0H (192 decimal), checking if we've passed the bitmap area.

5768

CALL NC,5240H D4 40 52

If the NC FLAG is set (past bitmap), CALL 5240H to handle overflow/wrap.

576B

INC C 0C

Increment the bit counter in Register C.

576C

LD B,C 41

Copy the bit counter to Register B for the rotation loop.

576D

LD A,7FH 3E 7F

Load Register A with 7FH (01111111 binary), a mask with bit 7 clear.

Rotate the mask to position the correct bit.

576F

RLCA 07

Rotate Register A left. This shifts the zero bit into position.

5770

DJNZ 576FH 10 FD

Decrement B and JUMP back to 576FH if not zero. [ROTATE LOOP]

5772

AND (HL) A6

AND the rotated mask with the bitmap byte at (HL), clearing the target bit to mark the sector as used.

5773

LD (HL),A 77

Store the updated bitmap byte back to memory.

5774

DEC DE 1B

Decrement the sector counter in DE.

5775

LD A,D 7A

Load Register A with the high byte of DE.

5776

OR E B3

OR with the low byte to test if DE has reached zero.

5777

JR Z,5751H 28 D8

If the Z FLAG is set (DE=0, all sectors marked), JUMP to 5751H to finish up.

5779

LD A,(59CAH) 3A CA 59

Load Register A with the sectors-per-track value from 59CAH.

577C

CP C B9

Compare with the current bit position in C.

577D

JR NZ,576BH 20 EC

If the NZ FLAG is set (more sectors in this track), JUMP back to 576BH to process next sector.

577F

LD C,00H 0E 00

Reset the bit counter to 0 for the new track.

5781

INC L 2C

Increment L to move to the next bitmap byte (next track).

5782

JR 5765H 18 E1

JUMP back to 5765H to continue processing. [LOOP]

5784H - Reserved/Padding Area

This area contains NOP instructions, likely reserved space or padding for alignment.

5784

NOP 00

No operation (padding byte).

5785

NOP 00

No operation (padding byte).

5786

NOP 00

No operation (padding byte).

5787

NOP 00

No operation (padding byte).

5788

NOP 00

No operation (padding byte).

5789

NOP 00

No operation (padding byte).

578AH - Initialize Verify Operation

This subroutine initializes the verify operation, setting up pointers and counters for verifying disk data. It's typically called after a FORMAT or COPY to verify the written data.

578A

LD A,20H 3E 20

Load Register A with 20H (32 decimal, space character or flag value).

578C

LD (57EBH),A 32 EB 57

Store this value at 57EBH (self-modifying code location - modifies the LD B,00H at 57EA to LD B,20H).

578F

LD (5B21H),DE ED 53 21 5B

Store Register DE at 5B21H (starting sector address for verify).

5793

LD HL,4200H 21 00 42

Load Register HL with 4200H, the address of the verify buffer area.

5796

LD (5B1AH),HL 22 1A 5B

Store HL at 5B1AH (verify buffer pointer).

5799

LD HL,(59CFH) 2A CF 59

Load Register HL with the total sector count from 59CFH.

579C

OR A B7

Clear the Carry flag by ORing A with itself.

579D

SBC HL,DE ED 52

Subtract DE (starting sector) from HL (total sectors) to get the number of sectors to verify.

579F

RET C D8

If the Carry FLAG is set (start > total, invalid range), RETURN immediately.

57A0

RET Z C8

If the Z FLAG is set (start = total, nothing to verify), RETURN immediately.

57A1

PUSH HL E5

Save the sector count onto the stack.

57A2

LD HL,5A79H 21 79 5A

Load HL with address 5A79H, pointing to the "VERIFYING" message string.

57A5

CALL 587EH CD 7E 58

CALL the message display routine at 587EH to show "VERIFYING" status.

57A8

LD HL,FFFFH 21 FF FF

Load Register HL with FFFFH (-1), used as an initialization value.

57AB

LD (5B23H),HL 22 23 5B

Store FFFFH at 5B23H (previous sector marker, -1 means none).

57AE

SET 1,(IX+00H) DD CB 00 CE

Set bit 1 of the byte at IX+0 (FCB flags), indicating verify mode is active.

57B2

POP HL E1

Restore the sector count from the stack.

[VERIFY LOOP] - Read and verify each sector.

57B3

CALL the disk read subroutine at 57C8H to read a sector.

57B6

JR Z,57BAH 28 02

If the Z FLAG is set (read successful), JUMP to 57BAH to continue.

57B8

CP 06H FE 06

Compare the error code with 06H (sector not found / end of data).

57BA

CALL NZ,585AH C4 5A 58

If the NZ FLAG is set (error other than 06H), CALL the error handler with retry prompt at 585AH.

57BD

JR NZ,57B3H 20 F4

If the NZ FLAG is set (user chose retry), JUMP back to 57B3H to retry the read. [RETRY LOOP]

57BF

DEC HL 2B

Decrement the remaining sector count.

57C0

CALL the progress indicator toggle routine at 571BH.

57C3

LD A,H 7C

Load Register A with the high byte of the sector count.

57C4

OR L B5

OR with the low byte to test if count has reached zero.

57C5

JR NZ,57B3H 20 EC

If the NZ FLAG is set (more sectors to verify), JUMP back to 57B3H. [MAIN LOOP]

57C7

RET C9

Return - all sectors verified successfully.

57C8H - Disk Read Subroutine

This subroutine reads a sector from disk using the FCB pointed to by IX. It's a wrapper that sets up the DE register and calls the SYS0 read routine.

57C8

PUSH IX DD E5

Push the IX register (FCB pointer) onto the stack.

57CA

POP DE D1

Pop the value into DE, effectively copying IX to DE.

57CB

JP 4436H C3 36 44

JUMP to the SYS0 sector read routine at 4436H with the FCB address in DE.

57CEH - Disk Write Subroutine

This subroutine writes a sector to disk using the FCB pointed to by IX. Similar to the read routine, it's a wrapper for the SYS0 write function.

57CE

PUSH IX DD E5

Push the IX register (FCB pointer) onto the stack.

57D0

POP DE D1

Pop the value into DE, copying IX to DE.

57D1

JP 5CE4H C3 E4 5C

JUMP to the sector write routine at 5CE4H with the FCB address in DE.

57D4H - Disk Write with Verify

This subroutine writes a sector and optionally verifies it. Uses IX as the FCB pointer.

57D4

PUSH IX DD E5

Push the IX register (FCB pointer) onto the stack.

57D6

POP DE D1

Pop the value into DE, copying IX to DE.

57D7

JP 443CH C3 3C 44

JUMP to the SYS0 write-with-verify routine at 443CH.

57DAH - Display Error Status

This subroutine displays an error status message on the screen, showing the error type and the affected file/sector. It saves all registers before displaying and restores them after.

57DA

PUSH HL E5

Save Register HL onto the stack.

57DB

PUSH DE D5

Save Register DE onto the stack.

57DC

PUSH BC C5

Save Register BC onto the stack.

57DD

PUSH AF F5

Save Register AF (accumulator and flags) onto the stack.

57DE

CALL the carriage return output routine at 5881H to start on a new line.

57E1

LD HL,59D3H 21 D3 59

Load HL with address 59D3H, pointing to the "ERROR WHILE " message string.

57E4

CALL the SYS0 string display routine at 4467H to print "ERROR WHILE ".

57E7

LD HL,5A67H 21 67 5A

Load HL with address 5A67H, pointing to "READING" message (default operation type).

57EA

LD B,00H 06 00

Load Register B with 00H. NOTE: This is self-modifying code - the 00H at 57EBH can be changed to 20H to select different messages.

57EC

BIT 6,B CB 70

Test bit 6 of Register B. If set, use "WRITING" message.

57EE

JR Z,57F3H 28 03

If the Z FLAG is set (bit 6 clear), JUMP to 57F3H to keep "READING" message.

57F0

LD HL,5A70H 21 70 5A

Load HL with address 5A70H, pointing to "WRITING" message string.

57F3

BIT 5,B CB 68

Test bit 5 of Register B. If set, use "VERIFYING" message.

57F5

JR Z,57FAH 28 03

If the Z FLAG is set (bit 5 clear), JUMP to 57FAH to use current message.

57F7

LD HL,5A79H 21 79 5A

Load HL with address 5A79H, pointing to "VERIFYING" message string.

57FA

CALL the SYS0 string display routine at 4467H to print the operation type.

57FD

LD HL,5A44H 21 44 5A

Load HL with address 5A44H, pointing to "DESTINATION" message.

5800

LD DE,(5B21H) ED 5B 21 5B

Load Register DE with the current sector number from 5B21H.

5804

BIT 7,B CB 78

Test bit 7 of Register B. If set, this is a source (not destination) operation.

5806

JR Z,580FH 28 07

If the Z FLAG is set (bit 7 clear, destination), JUMP to 580FH.

5808

LD HL,5A3CH 21 3C 5A

Load HL with address 5A3CH, pointing to "SOURCE" message.

580B

LD DE,(5AEFH) ED 5B EF 5A

Load Register DE with the source sector number from 5AEFH.

580F

CALL the string display routine to print "SOURCE" or "DESTINATION".

5812

LD HL,5A5FH 21 5F 5A

Load HL with address 5A5FH, pointing to "SECTOR" message.

5815

CALL the string display routine to print "SECTOR".

5818

CALL 5909H CD 09 59

CALL the decimal number display routine at 5909H to print the sector number in DE.

581B

CALL the carriage return routine to move to the next line.

581E

LD A,(5996H) 3A 96 59

Load Register A with the option flags from 5996H.

5821

BIT 2,A CB 57

Test bit 2 of the option flags. If set, suppress detailed error info.

5823

JP NZ,521EH C2 1E 52

If the NZ FLAG is set (suppress details), JUMP to 521EH to skip remaining output.

5826

CALL 5868H CD 68 58

CALL the disk error display routine at 5868H to show the detailed error message.

Continue the error display by showing the filename and prompting for retry.

5829

POP BC C1

Restore Register BC from the stack (saved at 57DCH). BC contains the sector/error count.

582A

LD HL,(593EH) 2A 3E 59

Load Register HL with the current drive pointer from 593EH.

582D

LD A,(4317H) 3A 17 43

Load Register A with the current drive number from SYS0 location 4317H.

5830

LD C,A 4F

Copy the drive number to Register C for later use.

5831

PUSH HL E5

Save the drive pointer onto the stack.

5832

PUSH BC C5

Save BC (with drive number in C) onto the stack.

5833

CALL 5582H CD 82 55

CALL the primary drive setup routine at 5582H to ensure the drive is properly selected.

5836

LD A,B 78

Load Register A with Register B (contains error flags from the drive setup).

5837

CALL 584AH CD 4A 58

CALL the error prompt display routine at 584AH to show retry/cancel options.

583A

POP BC C1

Restore BC (with drive number) from the stack.

583B

POP DE D1

Restore DE (the drive pointer that was in HL) from the stack.

583C

PUSH AF F5

Save the user response (from 584AH) onto the stack.

583D

LD A,C 79

Load Register A with the drive number from C.

583E

CALL the drive initialization routine at 568DH to reset the drive to its original state.

5841

EX DE,HL EB

Exchange DE and HL, putting the drive pointer back in HL.

5842

CALL 5585H CD 85 55

CALL the common drive setup routine at 5585H to finalize drive selection.

5845

POP AF F1

Restore the user response from the stack.

5846

POP BC C1

Restore Register BC from the stack (originally saved at 57DCH).

5847

POP DE D1

Restore Register DE from the stack (originally saved at 57DBH).

5848

POP HL E1

Restore Register HL from the stack (originally saved at 57DAH).

5849

RET C9

Return to the caller with the user response flags set (Z=retry, NZ=cancel).

584AH - Display Retry/Cancel Prompt

This subroutine displays a retry/cancel prompt after an error. It checks if user interaction is allowed and either prompts the user or automatically cancels. Register A on entry contains error flags; Register B contains operation flags.

584A

LD HL,5995H 21 95 59

Load HL with address 5995H, the option flags location.

584D

BIT 7,(HL) CB 7E

Test bit 7 of the option flags. If set, user interaction is disabled (batch mode).

584F

If the NZ FLAG is set (no interaction mode), JUMP to the error handler at 521AH to abort.

5852

OR 0C0HOR 11000000 F6 C0

OR Register A with C0H (11000000 binary), setting the high bits to indicate error type.

5854

CALL 4409H CD 09 44

CALL the SYS0 error display routine at 4409H to show the error code.

5857

JP 58C8H C3 C8 58

JUMP to 58C8H to display the retry/cancel prompt and get user response.

585AH - Error Handler with Retry Prompt

This is the main error handler that displays the error, prompts for retry, and optionally updates the error counter. Called when a disk error occurs during read/write/verify operations.

585A

CALL 57DAH CD DA 57

CALL the error status display routine at 57DAH to show the error details.

585D

RET NZ C0

If the NZ FLAG is set (user chose cancel or error handler returned with error), RETURN immediately.

User chose to retry. Increment the error counter at IX+0AH/0BH (16-bit counter).

585E

INC (IX+0AH) DD 34 0A

Increment the low byte of the error counter at IX+0AH (FCB offset 10).

5861

JR NZ,5866H 20 03

If the NZ FLAG is set (no overflow), JUMP to 5866H to skip high byte increment.

5863

INC (IX+0BH) DD 34 0B

Increment the high byte of the error counter at IX+0BH (FCB offset 11) on overflow.

5866

XOR A AF

Clear Register A to zero, setting the Z FLAG to indicate retry.

5867

RET C9

Return with Z FLAG set (indicating user chose retry).

5868H - Display Disk Error Message

This subroutine displays a detailed disk error message including the filename. The error code is expected in a self-modifying location (5869H). Returns NZ if an error was displayed.

5868

XOR A AF

Clear Register A to zero.

5869

OR 00H F6 00

Self-modifying code: The 00H at 586AH is replaced with the actual error code. OR sets flags based on the error code.

586B

RET Z C8

If the Z FLAG is set (error code is 0, no error), RETURN immediately.

586C

LD HL,59E0H 21 E0 59

Load HL with address 59E0H, pointing to the "WITHIN FILE" message string.

586F

CALL the SYS0 string display routine at 4467H to print "WITHIN FILE".

5872

CALL 56DDH CD DD 56

CALL the directory entry lookup routine at 56DDH to get the filename address.

5875

CALL 58A0H CD A0 58

CALL the filename display routine at 58A0H to print the filename.

5878

CALL the carriage return routine to move to the next line.

587B

OR FFH F6 FF

OR Register A with FFH, setting it to FFH and clearing the Z FLAG to indicate an error was displayed.

587D

RET C9

Return with NZ FLAG set.

587EH - Message Display Subroutine

This is a general-purpose message display routine that prints a string pointed to by HL, followed by a carriage return.

587E

CALL the SYS0 string display routine at 4467H to print the message string pointed to by HL.

Fall through to output a carriage return.

5881H - Output Carriage Return

This subroutine outputs a carriage return character (0DH) to move the cursor to the beginning of the next line.

5881

LD A,0DH 3E 0D

Load Register A with 0DH (ASCII carriage return).

5883

JP 58BDH C3 BD 58

JUMP to the character output routine at 58BDH to display the carriage return.

5886H - Display String with Control Characters Filtered

This subroutine displays B characters from the string at HL, converting control characters (below 20H) and high characters (80H and above) to spaces. Used for safe display of directory entries and user input.

5886

LD A,(HL) 7E

Load Register A with the character at the current position (HL).

5887

CP 20H FE 20

Compare Register A with 20H (space). Check if it's a control character.

5889

INC HL 23

Increment HL to point to the next character.

588A

JR C,5890H 38 04

If the Carry FLAG is set (character < 20H, control char), JUMP to 5890H to replace with space.

588C

CP 80H FE 80

Compare Register A with 80H. Check if it's a high character.

588E

JR C,5892H 38 02

If the Carry FLAG is set (character < 80H, normal printable), JUMP to 5892H to display it.

5890

LD A,20H 3E 20

Load Register A with 20H (space) to replace invalid characters.

5892

CALL the character output routine to display the character.

5895

DJNZ 5886H 10 EF

Decrement B and JUMP back to 5886H if not zero to process the next character. [LOOP]

5897

RET C9

Return after displaying all characters.

5898H - Display B Spaces

This subroutine displays B space characters. Used for padding output and alignment.

5898

LD A,20H 3E 20

Load Register A with 20H (ASCII space).

589A

CALL the character output routine to display a space.

589D

DJNZ 5898H 10 F9

Decrement B and JUMP back to 5898H if not zero. [LOOP]

589F

RET C9

Return after displaying all spaces.

58A0H - Display Filename from Directory Entry

This subroutine displays a filename in the format "FILENAME/EXT" from a directory entry. On entry, HL points to the directory entry. The filename is at offset +5 (8 characters) and extension at offset +13 (3 characters).

58A0

LD A,L 7D

Load Register A with the low byte of HL (directory entry pointer).

58A1

ADD 05H C6 05

Add 5 to Register A, calculating the offset to the filename within the directory entry.

58A3

LD L,A 6F

Store the result back in Register L. HL now points to the filename.

58A4

LD B,08H 06 08

Load Register B with 8, the length of the filename portion.

58A6

CALL 58B3H CD B3 58

CALL the display non-space characters routine at 58B3H to print the filename.

Now display the extension with a "/" separator if present.

58A9

LD A,(HL) 7E

Load Register A with the first character of the extension.

58AA

CP 20H FE 20

Compare with 20H (space). Check if extension exists.

58AC

LD B,03H 06 03

Load Register B with 3, the length of the extension.

58AE

LD A,2FH 3E 2F

Load Register A with 2FH (ASCII "/" slash) for the separator.

58B0

CALL NZ,58BDH C4 BD 58

If the NZ FLAG is set (extension exists, not space), CALL the output routine to print "/".

Fall through to display the extension characters.

58B3H - Display Non-Space Characters from String

This subroutine displays characters from the string at HL, skipping trailing spaces. B contains the maximum number of characters to check. Used for compact filename display.

58B3

LD A,(HL) 7E

Load Register A with the character at the current position.

58B4

CP 20H FE 20

Compare with 20H (space).

58B6

INC HL 23

Increment HL to the next character position.

58B7

CALL NZ,58BDH C4 BD 58

If the NZ FLAG is set (not a space), CALL the output routine to display the character.

58BA

DJNZ 58B3H 10 F7

Decrement B and JUMP back to 58B3H if not zero. [LOOP]

58BC

RET C9

Return after processing all characters.

58BDH - Character Output Routine

This is the low-level character output routine. It saves DE, calls the ROM display routine, and restores DE. Character to output is in Register A.

58BD

PUSH DE D5

Save Register DE onto the stack (ROM routine may modify it).

58BE

PUSH AF F5

Save Register AF (character and flags) onto the stack.

58BF

CALL 0033H CD 33 00

CALL the ROM character output routine at 0033H to display the character in A.

58C2

POP AF F1

Restore Register AF from the stack.

58C3

POP DE D1

Restore Register DE from the stack.

58C4

RET C9

Return to the caller.

58C5H - Display String and Prompt

This routine displays a string and then shows the retry/cancel prompt. Used for error messages that require user response.

58C5

CALL the SYS0 string display routine at 4467H to print the message at HL.

Fall through to display the retry/cancel prompt.

58C8H - Retry/Cancel Prompt Handler

This subroutine displays the "REPLY C (CANCEL), R (RETRY) OR P (PROCEED)" prompt and waits for user input. Returns Z flag set if user chose Retry, NZ if Cancel or Proceed.

58C8

LD A,(5995H) 3A 95 59

Load Register A with the option flags from 5995H.

58CB

BIT 7,A CB 7F

Test bit 7 of the option flags. If set, no user interaction is allowed.

58CD

JP NZ,5249H C2 49 52

If the NZ FLAG is set (no-interaction mode), JUMP to 5249H to handle automatically.

58D0

LD HL,5A84H 21 84 5A

Load HL with address 5A84H, pointing to the "CPR" (Cancel/Proceed/Retry) prompt options.

58D3

CALL 58E4H CD E4 58

CALL the menu prompt handler at 58E4H to display options and get user choice.

58D6

CP 01H FE 01

Compare the user's choice with 01H (Retry option index).

58D8

RET NC D0

If the NC FLAG is set (choice >= 1, Retry or Proceed), RETURN with appropriate flags.

58D9

LD A,39H 3E 39

Load Register A with error code 39H ("Operator Break/Cancel").

58DB

JUMP to the main error handler at 521AH with the cancel error.

58DEH - Yes/No Prompt Handler

This subroutine displays a yes/no prompt and returns the user's choice. Used for confirmation dialogs.

58DE

CALL the string display routine to print the prompt message at HL.

58E1

LD HL,5AB3H 21 B3 5A

Load HL with address 5AB3H, pointing to the "NY" (No/Yes) option string.

Fall through to the menu handler.

58E4H - Menu Prompt Handler

This is the general menu prompt handler. HL points to a null-terminated string of valid option characters. It displays the prompt, waits for a valid key, and returns the index of the chosen option in A (0-based).

58E4

PUSH BC C5

Save Register BC onto the stack.

58E5

PUSH HL E5

Save the option string pointer onto the stack.

Find the end of the option string to display the full prompt.

58E6

LD A,(HL) 7E

Load Register A with the character at the current position.

58E7

OR A B7

Test if A is zero (null terminator).

58E8

INC HL 23

Increment HL to the next character.

58E9

JR NZ,58E6H 20 FB

If the NZ FLAG is set (not at end), LOOP back to continue scanning. [SCAN LOOP]

58EB

CALL the string display routine. HL now points past the null, to the prompt text.

[INPUT LOOP] - Wait for a valid key press.

58EE

CALL 572BH CD 2B 57

CALL the keyboard check routine at 572BH to get a key press.

58F1

POP HL E1

Restore the option string pointer from the stack.

58F2

LD C,FFH 0E FF

Initialize the option index counter to FFH (-1, will be incremented to 0).

58F4

PUSH HL E5

Save the option string pointer again for the next iteration.

Search for the pressed key in the option string.

58F5

INC (HL) 34

Temporarily increment the byte at HL (used as a check mechanism).

58F6

INC C 0C

Increment the option index counter.

58F7

DEC (HL) 35

Restore the original value at HL.

58F8

JR Z,58EEH 28 F4

If the Z FLAG is set (byte was 0, end of options without match), LOOP back to wait for another key.

58FA

CP (HL) BE

Compare the pressed key (in A) with the current option character.

58FB

INC HL 23

Increment HL to the next option character.

58FC

JR NZ,58F5H 20 F7

If the NZ FLAG is set (no match), LOOP to check the next option.

Match found! Display the selected character and return.

58FE

CALL the character output routine to echo the selected option.

5901

CALL the carriage return routine to move to the next line.

5904

LD A,C 79

Load Register A with the option index from C.

5905

OR A B7

Set flags based on the option index (Z if index=0).

5906

POP HL E1

Clean up the stack (discard saved option pointer).

5907

POP BC C1

Restore Register BC from the stack.

5908

RET C9

Return with the option index in A and flags set accordingly.

5909H - Display Decimal Number

This subroutine displays the 16-bit number in DE as a decimal value. It uses a powers-of-10 table at 5933H to perform the conversion. Leading zeros are suppressed.

5909

LD BC,0400H 01 00 04

Load Register BC with 0400H. B=04 (4 digits to process for 10000s, 1000s, 100s, 10s), C=00 (leading zero flag).

590C

LD HL,5933H 21 33 59

Load HL with address 5933H, the powers-of-10 table (10000, 1000, 100, 10).

[DIGIT LOOP] - Process each decimal digit position.

590F

PUSH BC C5

Save the digit counter and leading zero flag.

5910

LD C,(HL) 4E

Load Register C with the low byte of the current power of 10.

5911

INC HL 23

Increment HL.

5912

LD B,(HL) 46

Load Register B with the high byte of the current power of 10. BC now contains the divisor.

5913

INC HL 23

Increment HL to point to the next power of 10.

5914

EX DE,HL EB

Exchange DE and HL. HL now contains the number, DE points to the table.

5915

LD A,2FH 3E 2F

Load Register A with 2FH (ASCII '0' minus 1). This will be incremented for each subtraction.

[SUBTRACTION LOOP] - Count how many times we can subtract the power of 10.

5917

INC A 3C

Increment the digit counter in A.

5918

ADD HL,BC 09

Add BC to HL. Wait - this should be SBC! Actually this adds the negative (BC contains negative value in two's complement context). Actually looking at the table, the values are stored normally. Let me reconsider...

5919

JR C,5917H 38 FC

If the Carry FLAG is set (result positive, subtraction succeeded), LOOP back to subtract again.

591B

SBC HL,BC ED 42

Subtract BC from HL with borrow to restore the previous value (undo one extra subtraction).

591D

POP BC C1

Restore the digit counter and leading zero flag.

591E

EX DE,HL EB

Exchange back. DE contains the remainder, HL points to the table.

591F

CP 30H FE 30

Compare the digit with 30H (ASCII '0'). Check if this is a zero digit.

5921

JR NZ,5927H 20 04

If the NZ FLAG is set (non-zero digit), JUMP to 5927H to display it.

5923

INC C 0C

Increment C (test if we've displayed any non-zero digit yet).

5924

DEC C 0D

Decrement C back. If C was 0, Z flag is set (leading zero, suppress).

5925

JR Z,592BH 28 04

If the Z FLAG is set (leading zero), JUMP to 592BH to skip displaying this digit.

5927

INC C 0C

Increment C to indicate we've displayed a non-zero digit (no more leading zero suppression).

5928

CALL the character output routine to display the digit.

592B

DJNZ 590FH 10 E2

Decrement B (digit counter) and LOOP back if more digits to process. [LOOP]

Display the final (units) digit.

592D

LD A,E 7B

Load Register A with the remainder (units digit) from E.

592E

ADD 30H C6 30

Add 30H to convert to ASCII.

5930

JP 58BDH C3 BD 58

JUMP to the character output routine to display the final digit and return.

5933H - Powers of 10 Table (DATA)

This table contains the powers of 10 used by the decimal display routine. Each entry is a 16-bit value stored in little-endian format. The values represent: -10000, -1000, -100, -10 (stored as two's complement negatives for the subtraction algorithm).

5933

DATA F0 D8

-10000 (D8F0H = -10000 in two's complement, or equivalently 55536 unsigned).

5935

DATA 18 FC

-1000 (FC18H = -1000 in two's complement).

5937

DATA 9C FF

-100 (FF9CH = -100 in two's complement).

5939

DATA F6 FF

-10 (FFF6H = -10 in two's complement).

593BH - System Variables and Buffers

This area contains system variables, flags, and buffer pointers used throughout the SYS6 FORMAT/COPY utility. Values shown are initial/default values; many are modified during operation.

593B

DATA 00

593BH: Reserved/scratch byte.

593C

DATA FF 6F

593CH-593DH: High memory pointer (default 6FFFH). Stores the top of available memory for buffers.

593E

DATA 42 59

593EH-593FH: Current drive parameter pointer (default points to 5942H).

5940

DATA 00 07

5940H-5941H: Option flags word. Bit 0: $ option present. Other bits control various FORMAT/COPY modes.

5942H - Drive Parameter Block Table

This table contains three 10-byte drive parameter blocks, one for each possible drive (0, 1, 2). Each block stores the drive status and buffer pointers. A value of FFH in the first byte indicates the drive slot is unused.

5942

DATA 00 01 00 00

Drive 0 Parameter Block (5942H-594BH): Status byte, flags, and pointers. 00H = active drive 0.

5946

DATA 99 59 99 59

Buffer pointers for drive 0 (pointing to 5999H).

594A

DATA 51 5A

Additional pointer/data for drive 0.

594C

DATA FF 02 E5 5A

Drive 1 Parameter Block (594CH-5955H): FFH in first byte = inactive/unused by default.

5950

DATA B7 59 A3 59

Buffer pointers for drive 1.

5954

DATA 3C 5A

Additional pointer/data for drive 1.

5956

DATA FF 04 17 5B

Drive 2 Parameter Block (5956H-595FH): FFH in first byte = inactive/unused by default.

595A

DATA C5 59 AD 59

Buffer pointers for drive 2.

595E

DATA 44 5A

Additional pointer/data for drive 2.

5960H - Filename Buffer Area

This area is used as a buffer for filename storage and manipulation during COPY operations. Initially filled with spaces (20H).

5960

DATA 20 20 20 20 20 20 20 20

Filename buffer (24 bytes of spaces): Used for temporary filename storage during file operations.

5968

DATA 20 20 20 20 20 20 20 20

Continuation of filename buffer.

5970

DATA 20 20 20 20 20 20 20 20

Continuation of filename buffer.

5978H - Disk Geometry Parameters

This area stores disk geometry and format parameters. These values are set during FORMAT initialization and used throughout disk operations.

5978

DATA 00 00 00 00

5978H-597BH: Reserved/padding bytes.

597C

DATA 08 08

597CH-597DH: Sectors per track values (default 8 for single density).

597E

DATA 82 00 00

597EH-5980H: Disk type flags and parameters. 82H indicates double-sided capability.

5981

DATA E0

5981H: Directory track/format flags.

5982H - Boot Sector Template

This is the boot sector name template that gets written to track 0 during FORMAT. Contains "BOOTNAME" followed by disk parameters.

5982

DATA 42 4E 4F 54 4E 41 4D 45 44

Boot sector name: ASCII "BNOTNAMED" - default disk name template.

598B

DATA 32 3A 2F 34 3A 2F 3A 3A 0D 00

Date template: ASCII "2:/4:/::" followed by CR and null - date format string.

5994H - Operation Mode Flags

These bytes control the operation mode of the FORMAT/COPY utility. They are set based on command line options and modified during execution.

5994

DATA 00

5994H: Primary mode flags. Bit 0: verify after write, Bit 6: no boot sector.

5995

DATA 00

5995H: User interaction flags. Bit 7: suppress user prompts (batch mode).

5996

DATA 00

5996H: Error handling flags. Bit 2: suppress detailed errors, Bit 5: continue on error.

5997

DATA 00

5997H: Additional option flags.

5999H - Scratch/Buffer Area

This large area (5999H-59D2H) serves as a scratch buffer and temporary storage area. It is used for sector data during read/write operations.

5999

DATA 00 00 00 ... (58 bytes)

Scratch buffer area: 58 bytes of working space for disk operations. Initialized to zeros.

59D3H - Message Strings

This area contains the ASCII message strings displayed by the FORMAT/COPY utility. Each string is terminated with a control character (03H) or null. The disassembler shows these as instructions but they are actually string data.

59D3

DATA "ERROR WHILE " 45 52 52 4F 52 20 57 48 49 4C 45 20 03

"ERROR WHILE " - Prefix for error messages during read/write/verify operations.

59E0

DATA "WITHIN FILE " 57 49 54 48 49 4E 20 46 49 4C 45 20 20 03

"WITHIN FILE " - Shown when an error occurs within a specific file.

59EE

DATA "PRESS \"ENTER\" WHEN " 50 52 45 53 53 20 22 45 4E 54 45 52 22 20 57 48 45 4E 20 03

"PRESS \"ENTER\" WHEN " - Prompt prefix for disk change requests.

5A02

DATA " DISKETTE MOUNTED ON DRIVE 0" 20 44 49 53 4B 45 54 54 45 20 4D 4F 55 4E 54 45 44 20 4F 4E 20 44 52 49 56 45 20 30 0D

" DISKETTE MOUNTED ON DRIVE 0" - Continuation of disk mount prompt.

5A1F

DATA "DONE" 44 4F 4E 45 0D

"DONE" - Success message after operation completes.

5A24

DATA "SOURCE & DEST SAME FILE" 53 4F 55 52 43 45 20 26 20 44 45 53 54 20 53 41 4D 45 20 46 49 4C 45 0D

"SOURCE & DEST SAME FILE" - Error when trying to copy a file onto itself.

5A3C

DATA "SOURCE " 53 4F 55 52 43 45 20 03

"SOURCE " - Label for source disk/file in COPY operations.

5A44

DATA "DESTINATION " 44 45 53 54 49 4E 41 54 49 4F 4E 20 03

"DESTINATION " - Label for destination disk/file in COPY operations.

5A51

DATA "** SYSTEM **" 2A 2A 20 53 59 53 54 45 4D 20 2A 2A 20 03

"** SYSTEM **" - Indicates a system file or disk.

5A5F

DATA "SECTOR " 53 45 43 54 4F 52 20 03

"SECTOR " - Prefix for sector number in error messages.

5A67

DATA "READING " 52 45 41 44 49 4E 47 20 03

"READING " - Operation type for error messages.

5A70

DATA "WRITING " 57 52 49 54 49 4E 47 20 03

"WRITING " - Operation type for error messages.

5A79

DATA "VERIFYING " 56 45 52 49 46 59 49 4E 47 20 03

"VERIFYING " - Operation type for verify phase.

5A84

DATA "CPR" 43 50 52 00

"CPR" - Menu options: Cancel, Proceed, Retry (null-terminated).

5A88

DATA "REPLY C (CANCEL), R (RETRY) OR P (PROCEED)" 52 45 50 4C 59 20 43 20 28 43 41 4E 43 45 4C 29 2C 20 52 20 28 52 45 54 52 59 29 20 4F 52 20 50 20 28 50 52 4F 43 45 45 44 29 0D

"REPLY C (CANCEL), R (RETRY) OR P (PROCEED)" - Retry/cancel prompt text.

5AB3

DATA "NY" 4E 59 00

"NY" - Menu options: No, Yes (null-terminated).

5AB6

DATA " (Y OR N) " 20 20 28 59 20 4F 52 20 4E 29 20 03

" (Y OR N) " - Yes/No prompt suffix.

5AC2

DATA "DISKETTE/GAT OVERFLOW" 44 49 53 4B 45 54 54 45 2F 47 41 54 20 4F 56 45 52 46 4C 4F 57 0D

"DISKETTE/GAT OVERFLOW" - Error when disk or Granule Allocation Table is full.

5AD8

DATA "DISK FULL - " 44 49 53 4B 20 46 55 4C 4C 20 2D 20 03

"DISK FULL - " - Error when destination disk runs out of space.

5AE5H - File Control Block (FCB) Template

This area contains the File Control Block used for disk I/O operations. It stores the current filename, extension, drive number, and sector information.

5AE5

DATA 82 20 00 00 42 00 00 FF 00 00

FCB Header: Drive/status (82H), flags, and initial parameters.

5AEF

DATA 00 00 00 00

5AEFH-5AF2H: Source sector pointer (used in COPY operations).

5AF3H - Sector Buffer Control Area

This area contains control structures for the sector buffer management. It tracks buffer allocation, dirty flags, and sector addresses.

This area contains an FFH-filled buffer used for sector data during COPY/BACKUP operations. The FFH bytes serve as uninitialized/available buffer space.

5AF3

DATA 5E 01 00 1F FF FF ...

Buffer control block: Pointers and status flags for sector buffering.

5AFF

DATA FF FF FF FF FF FF ...

Buffer pool: FFH-filled area used for sector data operation buffers (extends to ~5B50H).

5B17H - Destination File Control Block (FCB)

This is the second File Control Block used during COPY operations to track the destination file. It follows the same structure as the FCB at 5AE5H.

5B17

DATA 82 60 00 00 00 00 00 FF 00 00 00 00

Destination FCB: Status byte (82H=active), drive (60H), and file parameters. FF at offset 7 indicates no current sector loaded.

5B23

DATA FF FF 00 1F FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

5B23H-5B48H: Extended buffer space (38 bytes) for FCB operations and sector buffering.

5B49H - Third File Control Block (FCB)

A third FCB structure used for intermediate file operations during multi-file copy or backup operations.

5B49

DATA 82 60 00 00 42 00 00 FF 00 00 00 00 FF FF

Third FCB: Status (82H), drive (60H), file type (42H='B'), and parameters.

5B57H - Option Handler Dispatch Table

This table maps option codes to their handler routines. Each entry contains: option code, parameter bytes, and either inline code or a jump to the handler. The table is processed by the option parser at 55FBH to handle FORMAT/COPY command-line options.

5B57

DATA 02 00 64 5B

Option entry 02: Points to handler at 5B64H.

5B5B

DATA 04 00 A3 5B

Option entry 04: Points to handler at 5BA3H.

5B5F

DATA 05 00 E1 5B

Option entry 05: Points to handler at 5BE1H.

5B63

DATA 00

Table terminator: Zero marks end of dispatch table.

5B64H - Option Handler: DD (Double Density) Parameter

This handler processes double-density format parameters. The structure contains SYS0 function references and parameter values used during FORMAT operations.

5B64

DATA 3D 46 01 A8 41

Parameter block: 3DH marker, reference to 4641H (GAT handling), parameter 41A8H.

5B69

DATA 46 01 A9 37

Continuation: Additional parameters (4601H, 37A9H).

5B6D

DATA 47 03

Parameter 47H: Option flag with count 03H.

5B6F

JP 5C0BH C3 0B 5C

JUMP to 5C0BH to execute the DD option handler.

5B72H - Option Handler: Stepping Rate Parameter

This handler processes disk stepping rate parameters for the FDC (Floppy Disk Controller).

5B72

DATA 37 48 01 0D 77

Parameter block: 37H marker, reference to 4801H, stepping parameter 770DH.

5B77

DATA 48 03

Parameter 48H: Option flag with count 03H.

5B79

JP 5C3EH C3 3E 5C

JUMP to 5C3EH to execute the stepping rate handler.

5B7CH - Option Handler: Verify Parameter

This handler processes the verify flag for FORMAT/COPY operations.

5B7C

DATA 92 48 03

Parameter block: 92H marker, reference to 4803H (verify function).

5B7F

JP 5C43H C3 43 5C

JUMP to 5C43H to execute the verify option handler.

5B82H - Option Handler: Head Load/Sectors Per Track

This handler processes head load timing and sectors-per-track parameters.

5B82

DATA EE 48 01 00 F4

Parameter block: EEH marker, reference to 4801H, parameter F400H.

5B87

DATA 48 01 01 38

Continuation: Parameter 4801H, value 3801H.

5B8B

DATA 49 03

Parameter 49H: Option flag with count 03H.

5B8D

JP 5C1EH C3 1E 5C

JUMP to 5C1EH to execute the head load option handler.

5B90H - Option Handler: Track/Cylinder Parameters

This handler processes track count and cylinder configuration parameters.

5B90

DATA 88 4C 01 03 B3

Parameter block: 88H marker, reference to 4C01H, parameter B303H.

5B95

DATA 4C 01 03 7F

Continuation: Parameter 4C01H, value 7F03H.

5B99

DATA 4A 01 21 EB 56

Parameter 4AH: Points to 56EBH handler.

5B9E

DATA 01 CD 00 00 00

Additional parameters: Call vector and padding.

5BA3H - Option Handler: Buffer/Memory Parameters

This handler processes buffer size and memory allocation parameters for COPY operations.

5BA3

DATA B2 4E 01 50 D0

Parameter block: B2H marker, reference to 4E01H, buffer parameter D050H.

5BA8

DATA 4E 03 00 00 00

Continuation: Parameter 4E03H with padding.

5BAD

DATA 20 4E 01 AF 68

Parameter 20H: Reference to 4E01H, value 68AFH.

5BB2

DATA 4F 01 00 7B

Parameter 4FH: Value 7B00H.

5BB6

DATA 4F 01 1A AF

Continuation: Parameter 4F01H, value AF1AH.

5BBA

DATA 4F 01 00 0A

Continuation: Parameter 4F01H, value 0A00H.

5BBE

DATA 50 01 00 61

Parameter 50H: Value 6100H.

5BC2

DATA 50 03

Parameter 50H: Option flag with count 03H.

5BC4H - Inline Option Code: Name Validation

This inline code validates disk name parameters during FORMAT operations.

5BC4

LD A,1AH 3E 1A

Load 1AH (end-of-file marker) into Register A for comparison.

5BC6

OR A B7

Set flags based on A (always non-zero here).

5BC7

SUB 50H D6 50

Subtract 50H ('P') from A to check range.

5BC9

DATA 03

Parameter byte: Count or flag value.

5BCA

JP 5C5BH C3 5B 5C

JUMP to 5C5BH to continue name validation.

5BCDH - Option Handler: Directory Parameters

This handler processes directory entry count and allocation parameters.

5BCD

DATA 12 51 01 1A 55

Parameter block: 12H marker, reference to 5101H, parameter 551AH.

5BD2

DATA 51 04

Parameter 51H: Option flag with count 04H.

5BD4

LD HL,5CEFH 21 EF 5C

Load HL with address 5CEFH (directory parameter handler).

5BD7

RET C9

RETURN to caller with HL pointing to handler.

5BD8H - Option Handler: System Configuration

This handler processes system configuration parameters and memory mapping options.

5BD8

RST 28H EF

Call RST 28H - DOS function dispatcher.

5BD9

DATA 4D 03

Function 4DH: System configuration with count 03H.

5BDB

CALL 5C71H CD 71 5C

CALL 5C71H to process system memory parameters.

5BDE

DATA 00 00 00

Padding: Three null bytes for alignment.

5BE1H - Option Handler: Disk Geometry Parameters

This handler processes disk geometry parameters including sector size, track count, and side configuration.

5BE1

DATA 61 4E 01 0D 6C

Parameter block: 61H marker, reference to 4E01H, parameter 6C0DH.

5BE6

DATA 4E 01 00 CE

Continuation: Parameter 4E01H, value CE00H.

5BEA

DATA 4E 01 18 EF

Continuation: Parameter 4E01H, value EF18H.

5BEE

DATA 4E 02 35 56

Parameter 4EH: Reference to 5635H handler.

5BF2

DATA DA 4E 01 2F 8B

Parameter DAH: Reference to 4E01H, value 8B2FH.

5BF7

DATA 4E 01 18 72

Continuation: Parameter 4E01H, value 7218H.

5BFB

DATA 4E 03

Parameter 4EH: Option flag with count 03H.

5BFD

JP 5C69H C3 69 5C

JUMP to 5C69H to execute geometry parameter handler.

5C00H - Sector Size Configuration Data

This area contains configuration data for sector size settings. The values are used by the FORMAT command to set up disk parameters.

5C00

DATA 32 50 01 00 40 4E 01 13 00 00 00

Sector configuration block: Sector size parameters (256 bytes = 0100H at 5C03H), track parameters.

5C0BH - DD Option Handler: Double Density Processing

This routine handles the double-density option for FORMAT operations. It checks the current density setting and adjusts format parameters accordingly.

5C0B

EI FB

Enable interrupts to allow system operations during format setup.

5C0C

POP BC C1

Restore BC (contains option parsing state).

5C0D

JR NZ,5C19H 20 0A

If NZ FLAG (not zero), JUMP to 5C19H to check error code.

5C0F

LD A,(46C4H) 3A C4 46

Load drive configuration byte from 46C4H (current drive parameters).

5C12

AND 20HAND 00100000 E6 20

Mask with 20H to isolate double-density flag (bit 5).

5C14

JR NZ,5C1CH 20 06

If double-density is enabled, JUMP to 5C1CH to return success.

5C16

ADD 06H C6 06

Add 06H to A to create error code for single-density only drive.

5C18

RET C9

RETURN with error code in A.

5C19

CP 06H FE 06

Compare A with 06H (density not supported error).

5C1B

RET NZ C0

If not error 06H, RETURN with current error code.

5C1C

XOR A AF

Clear Register A (set to zero for success).

5C1D

RET C9

RETURN with A=0 indicating success.

5C1EH - Head Load Option Handler

This routine processes head load timing parameters for the FDC. It calculates the appropriate head load value based on drive capabilities and user settings.

5C1E

PUSH BC C5

Save BC (option parsing context) to the stack.

5C1F

PUSH HL E5

Save HL (parameter pointer) to the stack.

5C20

LD L,A 6F

Copy A (user-specified value) to L.

5C21

LD H,00H 26 00

Clear H to make HL = 00xxH (value in L only).

5C23

LD A,05H 3E 05

Load 05H into A (function code for head load calculation).

5C25

CALL 4CB4H (SYS0) - Calculate head load timing value.

5C28

LD H,A 67

Copy result to H (calculated head load value).

5C29

LD A,L 7D

Retrieve original user value from L.

5C2A

LD L,H 6C

Move calculated value from H to L.

5C2B

EX (SP),HL E3

Exchange HL with top of stack (swap with saved HL).

5C2C

INC A 3C

Increment A (adjust user value).

5C2D

INC A 3C

Increment A again (add 2 to original value).

5C2E

CP L BD

Compare adjusted user value with calculated value.

5C2F

CALL NZ,490AH C4 0A 49

If values differ, CALL 490AH (SYS0) to set head load parameter.

5C32

POP HL E1

Restore HL from the stack.

5C33

POP BC C1

Restore BC from the stack.

5C34

RET NZ C0

If NZ FLAG (error occurred), RETURN with error.

5C35

LD A,30H 3E 30

Load 30H ('0') into A for display offset calculation.

5C37

CALL 4C92H (SYS0) - Convert value to display format.

5C3A

LD A,L 7D

Load converted value from L into A.

5C3B

JP 4947H C3 47 49

JUMP to 4947H (SYS0) to store the head load parameter.

5C3EH - Stepping Rate Option Handler

This routine handles the stepping rate parameter for the FDC. It validates the stepping rate and configures the controller accordingly.

5C3E

EX AF,AF' 08

Exchange AF with alternate AF' (save current flags).

5C3F

DEC A 3D

Decrement A (adjust stepping rate value).

5C40

JP NZ,4838H C2 38 48

If NZ FLAG (value not zero), JUMP to 4838H (SYS0) to set stepping rate.

5C43H - Verify Option Handler

This routine handles the verify flag for FORMAT operations. When verify is enabled, each track is read back after writing to confirm data integrity.

5C43

POP AF F1

Discard return address from stack (unwinding call chain).

5C44

POP AF F1

Discard another return address from stack.

5C45

POP AF F1

Discard third return address from stack.

5C46

LD A,(48BBH) 3A BB 48

Load format status byte from 48BBH.

5C49

OR A B7

Test if status byte is zero.

5C4A

JP NZ,48B8H C2 B8 48

If NZ FLAG (status non-zero), JUMP to 48B8H (SYS0) error handler.

5C4D

LD A,(IX+07H) DD 7E 07

Load format parameter byte from FCB offset 07H.

5C50

LD (486AH),A 32 6A 48

Store format parameter to 486AH (format control variable).

5C53

LD A,64H 3E 64

Load 64H (100 decimal) - verify retry count.

5C55

CALL 49DDH CD DD 49

CALL 49DDH (SYS0) - Initialize verify operation.

5C58

JP 4813H C3 13 48

JUMP to 4813H (SYS0) to continue format with verify.

5C5BH - Name Validation Handler

This routine validates disk name parameters by scanning the input buffer for valid characters. Names can be up to 80 characters.

5C5B

LD B,50H 06 50

Load 50H (80 decimal) into B as maximum name length counter.

5C5D

LD A,(HL) 7E

[LOOP START] Load character from name buffer into A.

5C5E

OR A B7

Test if character is null (end of name).

5C5F

JP Z,50FEH CA FE 50

If Z FLAG (null terminator), JUMP to 50FEH - name complete.

5C62

INC HL 23

Advance to next character in name buffer.

5C63

DJNZ 5C5DH 10 F8

Decrement B and [LOOP] back to 5C5DH if not zero.

5C65

LD A,1AH 3E 1A

Load 1AH (EOF marker) - name too long error.

5C67

OR A B7

Set NZ flag to indicate error condition.

5C68

RET C9

RETURN with error (A=1AH, NZ flag set).

5C69H - Geometry Parameter Handler

This routine processes disk geometry parameters and updates the format configuration accordingly.

5C69

DEC E 1D

Decrement E (geometry parameter counter).

5C6A

JP NZ,4E62H C2 62 4E

If NZ FLAG (more parameters), JUMP to 4E62H (SYS0) to process next.

5C6D

INC HL 23

Advance HL past current parameter.

5C6E

JP 4E95H C3 95 4E

JUMP to 4E95H (SYS0) to finalize geometry setup.

5C71H - System Memory Parameter Handler

This routine reads system memory configuration values and stores them in the format parameter block.

5C71

INC HL 23

Advance HL to parameter storage location.

5C72

LD A,(4046H) 3A 46 40

Load high memory pointer high byte from 4046H.

5C75

LD (HL),A 77

Store high byte to parameter block.

5C76

INC HL 23

Advance to next storage location.

5C77

LD A,(4044H) 3A 44 40

Load high memory pointer low byte from 4044H.

5C7A

LD (HL),A 77

Store low byte to parameter block.

5C7B

DEC HL 2B

Move back to first byte.

5C7C

DEC HL 2B

Move back to parameter start.

5C7D

JP 4E1FH C3 1F 4E

JUMP to 4E1FH (SYS0) to continue parameter processing.

5C80H - Set Up Sector Size (Returns BC=256)

This routine sets up the sector size parameter. For standard TRS-80 disks, this returns BC=0100H (256 bytes per sector).

5C80

LD BC,0100H 01 00 01

Load BC with 0100H (256 decimal) - standard sector size.

5C83

OR A B7

Test A register and set flags.

5C84

RET NZ C0

If NZ FLAG (A non-zero), RETURN with BC=256.

5C85

INC DE 13

Advance DE to sector size field in parameter block.

5C86

INC DE 13

Advance DE again (2-byte offset).

5C87

LD A,(DE) 1A

Load sector size code from parameter block.

5C88

LD (64BCH),A 32 BC 64

Store sector size code to 64BCH (format parameter table).

5C8B

DEC DE 1B

Move DE back to original position.

5C8C

DEC DE 1B

Move DE back (restore original pointer).

5C8D

RET C9

RETURN with sector size configured.

5C8EH - Set Up Sector Buffer Address

This routine stores the sector buffer address and sets the FCB flag to indicate the buffer is configured.

5C8E

LD (5B1AH),HL 22 1A 5B

Store HL (buffer address) to 5B1AH (destination FCB buffer pointer).

5C91

SET 6,(IX+01H) DD CB 01 F6

Set bit 6 of FCB+01H to indicate buffer is allocated.

5C95

RET C9

RETURN to caller.

5C96H - FORMAT Initialization

This routine initializes FORMAT operation parameters by reading source and destination drive configurations and checking for compatibility. It sets up the option dispatch table pointers for double-sided disk operations.

5C96

CALL 63B3H CD B3 63

CALL 63B3H to initialize format parameter tables.

5C99

LD A,(59BEH) 3A BE 59

Load source drive configuration byte from 59BEH.

5C9C

LD B,A 47

Copy source config to B for later comparison.

5C9D

LD A,(59B9H) 3A B9 59

Load source drive flags from 59B9H.

5CA0

LD C,A 4F

Copy source flags to C.

5CA1

LD A,(59CCH) 3A CC 59

Load destination drive configuration byte from 59CCH.

5CA4

LD D,A 57

Copy destination config to D.

5CA5

LD A,(59C7H) 3A C7 59

Load destination drive flags from 59C7H.

5CA8

LD E,A 5F

Copy destination flags to E. Now BC=source, DE=destination.

5CA9

LD A,C 79

Load source flags into A.

5CAA

AND E A3

AND with destination flags to find common capabilities.

5CAB

BIT 5,A CB 6F

Test bit 5 (double-sided capability) in both drives.

5CAD

JR Z,5CB5H 28 06

If Z FLAG (not both double-sided), JUMP to 5CB5H.

5CAF

LD A,B 78

Load source configuration into A.

5CB0

XOR D AA

XOR with destination configuration to find differences.

5CB1

RRCA 0F

Rotate right to move bit 0 to Carry flag.

5CB2

JP C,6747H DA 47 67

If Carry (configurations differ), JUMP to 6747H - incompatible drives error.

5CB5

LD A,B 78

Load source configuration back into A.

5CB6

BIT 5,C CB 69

Test bit 5 of source flags (double-sided source).

5CB8

JR NZ,5CBEH 20 04

If NZ FLAG (source is double-sided), JUMP to 5CBEH.

5CBA

BIT 5,E CB 6B

Test bit 5 of destination flags (double-sided dest).

5CBC

RET Z C8

If Z FLAG (destination single-sided), RETURN - no double-sided setup needed.

5CBD

LD A,D 7A

Load destination configuration into A.

5CBE

RRCA 0F

Rotate right to test bit 0.

5CBF

RET C D8

If Carry (bit 0 set), RETURN - already configured.

The following code sets up dispatch table pointers for double-sided disk operations by redirecting option handlers to the appropriate routines.

5CC0

LD HL,5B5BH 21 5B 5B

Load HL with address 5B5BH (option entry 04 pointer).

5CC3

LD (55F7H),HL 22 F7 55

Store to 55F7H - redirect option handler entry.

5CC6

LD HL,5BB1H 21 B1 5B

Load HL with address 5BB1H (buffer parameter entry).

5CC9

LD (5B5DH),HL 22 5D 5B

Store to 5B5DH - update option table pointer.

5CCC

LD HL,5C00H 21 00 5C

Load HL with address 5C00H (sector config data).

5CCF

LD (5B61H),HL 22 61 5B

Store to 5B61H - update sector config pointer.

5CD2

XOR A AF

Clear Register A to zero.

5CD3

LD (617FH),A 32 7F 61

Store zero to 617FH (clear side flag).

5CD6

LD H,A 67

Copy zero to H.

5CD7

LD L,A 6F

Copy zero to L. HL now = 0000H.

5CD8

LD (61BFH),HL 22 BF 61

Store zero to 61BFH (clear track counter).

5CDB

LD (5BB5H),HL 22 B5 5B

Store zero to 5BB5H (clear option parameter).

5CDE

LD A,18H 3E 18

Load 18H (24 decimal) - default sector count.

5CE0

LD (612DH),A 32 2D 61

Store to 612DH (sectors per track parameter).

5CE3

RET C9

RETURN with double-sided parameters configured.

5CE4H - DOS Configuration Check

This routine checks the DOS configuration flags and sets FCB parameters based on system capabilities.

5CE4

LD A,(430CH) 3A 0C 43

Load DOS configuration byte from 430CH.

5CE7

BIT 5,A CB 6F

Test bit 5 (extended disk support flag).

5CE9

JR Z,5CEFH 28 04

If Z FLAG (not extended), JUMP to 5CEFH.

5CEB

SET 5,(IX+02H) DD CB 02 EE

Set bit 5 of FCB+02H to enable extended mode.

5CEF

JP 4439H C3 39 44

JUMP to 4439H (SYS0) to continue configuration.

5CF2H - Extended Mode Sector Count Check

This routine checks if extended disk mode is active and returns the appropriate sector count multiplier.

5CF2

BIT 5,(IX+02H) DD CB 02 6E

Test bit 5 of FCB+02H (extended mode flag).

5CF6

JR Z,5CFCH 28 04

If Z FLAG (not extended mode), JUMP to 5CFCH.

5CF8

BIT 0,(IX+07H) DD CB 07 46

Test bit 0 of FCB+07H (sector size indicator).

5CFC

JP Z,4CB2H CA B2 4C

If Z FLAG (standard sectors), JUMP to 4CB2H (SYS0).

5CFF

LD A,03H 3E 03

Load 03H into A (extended sector count multiplier).

5D01

JP 4CB4H C3 B4 4C

JUMP to 4CB4H (SYS0) with multiplier in A.

5D04H - Scratch Area / Reserved Space

This area contains 13 bytes of zeros used as scratch space or reserved for future use. Some bytes may be modified during FORMAT operations.

5D04

DATA 00 00 00 00 00 00 00 00 00 00 00 00 00

5D04H-5D10H: 13 bytes of scratch/reserved space.

5D11H - PDRIVE/AUTO Processing Variables

This area contains variables for processing PDRIVE (physical drive) and AUTO configuration parameters during FORMAT with system disk creation.

5D11

DATA 42

5D11H: Default parameter value (42H = 'B').

5D12

DATA 16 5D

5D12H: Pointer to AUTO command buffer (initially 5D16H).

5D14

DATA 16 5D

5D14H: Secondary pointer to AUTO command buffer.

5D16H - FORMAT System Disk Initialization

This routine handles the initialization for creating a system disk during FORMAT. It clears FCB flags, checks for PDRIVE/AUTO options, and sets up the source drive for file copying.

5D16

CALL 6643H CD 43 66

CALL 6643H to initialize system file parameters.

5D19

LD HL,5AE5H 21 E5 5A

Load HL with address of primary FCB at 5AE5H.

5D1C

RES 1,(HL) CB 8E

Clear bit 1 of FCB status (reset file open flag).

5D1E

LD HL,5B17H 21 17 5B

Load HL with address of secondary FCB at 5B17H.

5D21

RES 1,(HL) CB 8E

Clear bit 1 of secondary FCB status.

5D23

LD A,(5997H) 3A 97 59

Load option flags from 5997H.

5D26

AND 30H E6 30

Mask with 30H to isolate PDRIVE/AUTO bits (bits 4-5).

5D28

JR Z,5D86H 28 5C

If Z FLAG (no PDRIVE/AUTO), JUMP to 5D86H to skip special handling.

5D2A

CALL 568BH CD 8B 56

CALL 568BH to set up primary drive for reading.

5D2D

LD HL,6491H 21 91 64

Load HL with address of input buffer at 6491H.

5D30

LD DE,4480H 11 80 44

Load DE with address of command line buffer at 4480H.

5D33

LD A,(448CH) 3A 8C 44

Load command line length from 448CH.

5D36

CP 0BH FE 0B

Compare with 0BH (11) - minimum valid length.

5D38

JR NC,5D65H 30 2B

If NC (length >= 11), JUMP to 5D65H - invalid parameter.

The following loop reads the AUTO/PDRIVE command string from the terminal, validating each character.

5D3A

LD B,0DH 06 0D

[LOOP START] Load B with 0DH (13) - max parameter length.

5D3C

CALL 5D71H CD 71 5D

CALL 5D71H to read next character from input.

5D3F

JR Z,5D3AH 28 F9

If Z FLAG (carriage return), [LOOP] back to 5D3AH for new line.

5D41

CP 20H FE 20

Compare with 20H (space character).

5D43

JR Z,5D3AH 28 F5

If Z FLAG (space), [LOOP] back to 5D3AH to skip whitespace.

5D45

CP 3BH FE 3B

Compare with 3BH (semicolon - comment marker).

5D47

JR NZ,5D53H 20 0A

If NZ FLAG (not semicolon), JUMP to 5D53H to store character.

Handle comment - skip to end of line.

5D49

CALL 5D71H CD 71 5D

[SKIP COMMENT LOOP] Read next character.

5D4C

JR NZ,5D49H 20 FB

If NZ FLAG (not carriage return), [LOOP] back to 5D49H.

5D4E

JR 5D3AH 18 EA

JUMP back to 5D3AH for next line.

Store valid characters and validate filename format.

5D50

CALL 5D71H CD 71 5D

[CHARACTER LOOP] Read next character.

5D53

LD (HL),A 77

Store character in buffer.

5D54

INC HL 23

Advance buffer pointer.

5D55

JR Z,5D3AH 28 E3

If Z FLAG (end of line), [LOOP] back to 5D3AH.

5D57

SUB 2FH D6 2F

Subtract 2FH ('/' - 1) to normalize for digit check.

5D59

CP 0BH FE 0B

Compare with 0BH (check if digit 0-9 or ':').

5D5B

JR C,5D63H 38 06

If Carry (valid digit/colon), JUMP to 5D63H.

5D5D

SUB 12H D6 12

Subtract 12H to check for letter A-Z.

5D5F

CP 1AH FE 1A

Compare with 1AH (26 letters).

5D61

JR NC,5D65H 30 02

If NC (invalid character), JUMP to 5D65H - error.

5D63

DJNZ 5D50H 10 EB

Decrement B and [LOOP] back to 5D50H if not zero.

Error handler - invalid AUTO/PDRIVE parameter.

5D65

LD A,01H 3E 01

Load 01H into A - error code 1 (invalid parameter).

5D67

PUSH AF F5

Save error code to stack.

5D68

LD HL,6283H 21 83 62

Load HL with address of error message at 6283H.

5D6B

CALL 4467H (SYS0) to display error message.

5D6E

JP 521BH C3 1B 52

JUMP to 521BH - error exit handler.

5D71H - Read Character from Input

This subroutine reads a single character from the input stream, handling special cases like BREAK key and end-of-file. Returns Z flag set if carriage return (end of line).

5D71

CALL 0013H CD 13 00

CALL 0013H (ROM) - Read character from input device.

5D74

JR NZ,5D7DH 20 07

If NZ FLAG (special condition), JUMP to 5D7DH.

5D76

AND 7FHAND 01111111 E6 7F

Mask off high bit (convert to 7-bit ASCII).

5D78

JR Z,5D71H 28 F7

If Z FLAG (null character), [LOOP] back to read another.

5D7A

CP 0DH FE 0D

Compare with 0DH (carriage return).

5D7C

RET C9

RETURN with Z flag indicating if CR was received.

Handle special input condition (EOF or BREAK).

5D7D

CP 1CH FE 1C

Compare with 1CH (end-of-file marker).

5D7F

JR NZ,5D67H 20 E6

If NZ FLAG (not EOF), JUMP to 5D67H - error handler.

5D81

LD A,0DH 3E 0D

Load 0DH (carriage return) into A.

5D83

LD (HL),A 77

Store CR in buffer to terminate string.

5D84

INC HL 23

Advance buffer pointer.

5D85

LD (HL),A 77

Store second CR (double-terminate).

5D86H - Continue FORMAT Drive Setup

This routine continues the FORMAT drive setup by initializing the source drive parameters and calculating buffer space.

5D86

CALL 5578H to set up source drive for FORMAT.

5D89

CALL 6162H CD 62 61

CALL 6162H to read disk parameters from source.

5D8C

CALL 6178H CD 78 61

CALL 6178H to calculate sectors per track.

5D8F

LD (597CH),A 32 7C 59

Store sectors per track to 597CH.

5D92

LD A,C 79

Load track count from C.

5D93

LD (59C0H),A 32 C0 59

Store track count to 59C0H.

5D96

LD HL,(593CH) 2A 3C 59

Load high memory limit from 593CH.

5D99

LD DE,FFE8H 11 E8 FF

Load DE with FFE8H (-24 decimal) adjustment.

5D9C

ADD HL,DE 19

Subtract 24 from high memory to create safety margin.

5D9D

LD (61DBH),HL 22 DB 61

Store adjusted limit to 61DBH (buffer ceiling).

5DA0

LD A,(5997H) 3A 97 59

Load option flags from 5997H.

5DA3

AND 30H E6 30

Mask with 30H to isolate PDRIVE/AUTO bits.

5DA5

JR Z,5E0FH 28 68

If Z FLAG (no special options), JUMP to 5E0FH.

5DA7

AND 10H E6 10

Mask with 10H to isolate PDRIVE bit only.

5DA9

LD C,A 4F

Copy PDRIVE flag to C.

5DAA

JR Z,5DB5H 28 09

If Z FLAG (AUTO only), JUMP to 5DB5H.

Clear the track table for PDRIVE operation.

5DAC

XOR A AF

Clear A to zero.

5DAD

LD B,A 47

Copy zero to B (will wrap to 256 iterations).

5DAE

LD HL,6291H 21 91 62

Load HL with address of track table at 6291H.

5DB1

LD (HL),A 77

[LOOP START] Store zero to track table entry.

5DB2

INC HL 23

Advance to next entry.

5DB3

DJNZ 5DB1H 10 FC

Decrement B and [LOOP] back if not zero (256 iterations).

5DB5H - Process AUTO/PDRIVE File List

This routine processes the file list for AUTO command or PDRIVE configuration, opening each file specified in the input buffer.

5DB5

LD HL,6491H 21 91 64

Load HL with address of input buffer at 6491H.

5DB8

LD A,(HL) 7E

[FILE LOOP] Load current character from buffer.

5DB9

CP 0DH FE 0D

Compare with 0DH (carriage return).

5DBB

JR Z,5E07H 28 4A

If Z FLAG (end of list), JUMP to 5E07H.

5DBD

LD DE,447FH 11 7F 44

Load DE with address of filename buffer at 447FH.

Copy filename from input buffer to filename buffer.

5DC0

INC DE 13

[COPY LOOP] Advance destination pointer.

5DC1

LD A,(HL) 7E

Load character from source.

5DC2

CP 0DH FE 0D

Compare with 0DH (carriage return).

5DC4

LD (DE),A 12

Store character to destination.

5DC5

INC HL 23

Advance source pointer.

5DC6

JR NZ,5DC0H 20 F8

If NZ FLAG (not CR), [LOOP] back to 5DC0H.

Append drive number to filename.

5DC8

EX DE,HL EB

Exchange DE and HL (HL now points to end of filename).

5DC9

LD (HL),3AH 36 3A

Store 3AH (':') as drive separator.

5DCB

INC HL 23

Advance to drive number position.

5DCC

LD A,(594CH) 3A 4C 59

Load source drive number from 594CH.

5DCF

LD B,64H 06 64

Load B with 64H (100) for decimal conversion.

5DD1

CALL 61CBH CD CB 61

CALL 61CBH to convert hundreds digit.

5DD4

LD B,0AH 06 0A

Load B with 0AH (10) for decimal conversion.

5DD6

CALL 61CBH CD CB 61

CALL 61CBH to convert tens digit.

5DD9

ADD 30H C6 30

Add 30H ('0') to convert units to ASCII.

5DDB

LD (HL),A 77

Store units digit.

5DDC

INC HL 23

Advance pointer.

5DDD

LD (HL),0DH 36 0D

Store 0DH (CR) to terminate filename.

5DDF

EX DE,HL EB

Exchange DE and HL (restore pointers).

5DE0

LD DE,4480H 11 80 44

Load DE with filename buffer address again.

5DE3

CALL 4424H CD 24 44

CALL 4424H (SYS0) - Open file by name.

5DE6

JR Z,5DF1H 28 09

If Z FLAG (success), JUMP to 5DF1H.

5DE8

CP 18H FE 18

Compare error code with 18H (file not found).

5DEA

JR Z,5DB8H 28 CC

If Z FLAG (not found), [LOOP] back to try next file.

5DEC

CP 19H FE 19

Compare with 19H (end of directory).

5DEE

If NZ FLAG (other error), JUMP to 521AH - error handler.

5DF1H - Record File Track in Table

This routine records the track number of an opened file in the track table for later copying during system disk creation.

5DF1

LD A,(4F56H) 3A 56 4F

Load current track number from 4F56H.

5DF4

PUSH HL E5

Save HL (input buffer pointer) to stack.

5DF5

LD HL,6291H 21 91 62

Load HL with address of track table at 6291H.

5DF8

LD E,A 5F

Copy track number to E.

5DF9

LD D,00H 16 00

Clear D for 16-bit offset.

5DFB

ADD HL,DE 19

Add track number as offset to table base.

5DFC

LD A,C 79

Load PDRIVE flag from C.

5DFD

OR A B7

Test if PDRIVE mode.

5DFE

JR Z,5E03H 28 03

If Z FLAG (AUTO mode), JUMP to 5E03H.

5E00

LD A,(4D6EH) 3A 6E 4D

Load PDRIVE parameter from 4D6EH.

5E03

LD (HL),A 77

Store track marker in table.

5E04

POP HL E1

Restore input buffer pointer from stack.

5E05

JR 5DB8H 18 B1

JUMP back to 5DB8H to process next file.

5E07H - Finish AUTO/PDRIVE Processing

This routine completes the AUTO/PDRIVE file list processing and returns to normal FORMAT operation.

5E07

LD A,05H 3E 05

Load 05H into A (function code).

5E09

CALL 568DH to flush drive buffers.

5E0C

CALL 5578H to reset source drive setup.

5E0FH - Initialize AUTO Command Pointers

This routine initializes the AUTO command buffer pointers for system disk operations.

5E0F

LD HL,6491H 21 91 64

Load HL with address of input buffer at 6491H.

5E12

LD (5D12H),HL 22 12 5D

Store to 5D12H (AUTO command pointer 1).

5E15

LD (5D14H),HL 22 14 5D

Store to 5D14H (AUTO command pointer 2).

5E18

LD C,00H 0E 00

Load C with 00H (initial track counter).

5E1A

CALL 619DH CD 9D 61

CALL 619DH to initialize track buffer.

5E1D

JP NZ,5EAAH C2 AA 5E

If NZ FLAG (error), JUMP to 5EAAH.

5E20

CALL 61F6H to read directory sector.

5E23

LD A,(5996H) 3A 96 59

Load option flags from 5996H.

5E26

JR NZ,5E32H 20 0A

If NZ FLAG (read error), JUMP to 5E32H.

5E28

BIT 0,A CB 47

Test bit 0 of option flags.

5E2A

JR Z,5E32H 28 06

If Z FLAG (bit 0 clear), JUMP to 5E32H.

5E2C

INC HL 23

Advance HL to check directory entry.

5E2D

BIT 5,(HL) CB 6E

Test bit 5 of directory entry (system flag).

5E2F

DEC HL 2B

Move back to start of entry.

5E30

JR Z,5EAAH 28 78

If Z FLAG (not system), JUMP to 5EAAH.

5E32

BIT 4,A CB 67

Test bit 4 of option flags.

5E34

JR Z,5E3EH 28 08

If Z FLAG (bit 4 clear), JUMP to 5E3EH.

5E36H - Check Directory Entry Flags

This code checks directory entry flags to determine if the entry should be processed during FORMAT/COPY operations.

5E36

BIT 6,(HL) CB 76

Test bit 6 of directory entry (invisible/hidden flag).

5E38

JR NZ,5EAAH 20 70

If NZ FLAG (hidden file), JUMP to 5EAAH to skip.

5E3A

BIT 3,(HL) CB 5E

Test bit 3 of directory entry (system file flag).

5E3C

JR NZ,5EAAH 20 6C

If NZ FLAG (system file), JUMP to 5EAAH to skip.

5E3E

BIT 1,A CB 4F

Test bit 1 of option flags (extension filter active).

5E40

JR Z,5E5BH 28 19

If Z FLAG (no filter), JUMP to 5E5BH.

Compare file extension with filter pattern.

5E42

PUSH HL E5

Save directory entry pointer to stack.

5E43

PUSH DE D5

Save DE to stack.

5E44

PUSH BC C5

Save BC to stack.

5E45

LD DE,000DH 11 0D 00

Load DE with 0DH (13) - offset to file extension.

5E48

ADD HL,DE 19

Add offset to point to extension field.

5E49

LD DE,624CH 11 4C 62

Load DE with address of extension filter pattern at 624CH.

5E4C

LD B,03H 06 03

Load B with 03H - extension length (3 characters).

5E4E

LD A,(DE) 1A

[COMPARE LOOP] Load filter character.

5E4F

CP (HL) BE

Compare with file extension character.

5E50

INC DE 13

Advance filter pointer.

5E51

INC HL 23

Advance extension pointer.

5E52

JR NZ,5E56H 20 02

If NZ FLAG (mismatch), JUMP to 5E56H.

5E54

DJNZ 5E4EH 10 F8

Decrement B and [LOOP] if not zero.

5E56

POP BC C1

Restore BC from stack.

5E57

POP DE D1

Restore DE from stack.

5E58

POP HL E1

Restore directory entry pointer from stack.

5E59

JR NZ,5EAAH 20 4F

If NZ FLAG (extension mismatch), JUMP to 5EAAH to skip file.

5E5BH - Process Valid Directory Entry

This routine processes a valid directory entry that passed all filters, checking for additional conditions like password protection.

5E5B

LD D,(HL) 56

Load directory entry status byte into D.

5E5C

BIT 6,D CB 72

Test bit 6 (password protected flag).

5E5E

CALL NZ,61EAH C4 EA 61

If NZ FLAG (protected), CALL 61EAH to handle password.

5E61

JR NZ,5EAAH 20 47

If NZ FLAG (password failed), JUMP to 5EAAH.

5E63

LD A,(5995H) 3A 95 59

Load additional option flags from 5995H.

5E66

BIT 6,A CB 77

Test bit 6 (confirmation prompt flag).

5E68

JR Z,5E87H 28 1D

If Z FLAG (no prompt), JUMP to 5E87H.

Display confirmation prompt for this file.

5E6A

PUSH DE D5

Save DE to stack.

5E6B

PUSH BC C5

Save BC to stack.

5E6C

CALL 58A0H CD A0 58

CALL 58A0H to display filename.

5E6F

LD HL,625CH 21 5C 62

Load HL with address of confirmation prompt at 625CH.

5E72

CALL 58E4H CD E4 58

CALL 58E4H to display prompt and get response.

5E75

POP BC C1

Restore BC from stack.

5E76

POP DE D1

Restore DE from stack.

5E77

JR NZ,5E81H 20 08

If NZ FLAG (response not default), JUMP to 5E81H.

5E79

LD HL,6D5EH 21 5E 6D

Load HL with address of skip message at 6D5EH.

5E7C

CALL 4467H (SYS0) to display message.

5E7F

JR 5E0FH 18 8E

JUMP back to 5E0FH to restart with next file.

5E81

DEC A 3D

Decrement A (check response code).

5E82

JR Z,5EB3H 28 2F

If Z FLAG (response = 1, proceed), JUMP to 5EB3H.

5E84

DEC A 3D

Decrement A again.

5E85

JR Z,5EAAH 28 23

If Z FLAG (response = 2, skip), JUMP to 5EAAH.

5E87H - Store Directory Entry in Track List

This routine stores the directory entry information in the track list for later processing during FORMAT/COPY operations.

5E87

LD HL,(5D14H) 2A 14 5D

Load HL with track list pointer from 5D14H.

5E8A

LD (HL),80H 36 80

Store 80H as entry marker (indicates valid entry).

5E8C

BIT 6,D CB 72

Test bit 6 of directory status (password protected).

5E8E

JR Z,5EA2H 28 12

If Z FLAG (not protected), JUMP to 5EA2H.

5E90

LD A,(5997H) 3A 97 59

Load option flags from 5997H.

5E93

BIT 3,A CB 5F

Test bit 3 (preserve password flag).

5E95

JR NZ,5EA2H 20 0B

If NZ FLAG (preserve), JUMP to 5EA2H.

5E97

LD A,C 79

Load track number into A.

5E98

CP 80H FE 80

Compare with 80H (128).

5E9A

JR NC,5EA2H 30 06

If NC (track >= 128), JUMP to 5EA2H.

5E9C

AND 18H E6 18

Mask with 18H to check track range.

5E9E

JR NZ,5EA2H 20 02

If NZ FLAG (not in range), JUMP to 5EA2H.

5EA0

SET 6,(HL) CB F6

Set bit 6 of track entry marker (flag for processing).

5EA2

INC HL 23

Advance track list pointer.

5EA3

LD (HL),C 71

Store track number low byte.

5EA4

INC HL 23

Advance pointer.

5EA5

LD (HL),B 70

Store track number high byte.

5EA6

INC HL 23

Advance pointer.

5EA7

LD (5D14H),HL 22 14 5D

Update track list pointer at 5D14H.

5EAAH - Advance to Next Directory Entry

This routine advances to the next directory entry and checks if there are more entries to process.

5EAA

LD HL,597CH 21 7C 59

Load HL with address of sectors per track counter at 597CH.

5EAD

CALL 61BAH CD BA 61

CALL 61BAH to advance sector counter.

5EB0

JP NC,5E1AH D2 1A 5E

If NC (more sectors), JUMP back to 5E1AH to continue.

5EB3H - Begin Track Processing

This routine begins processing the collected track list, reading and copying data from source to destination.

5EB3

CALL 6190H to reset track position.

5EB6

CALL 5699H to check end-of-disk condition.

5EB9

JP Z,552DH CA 2D 55

If Z FLAG (end of disk), JUMP to 552DH to finish.

5EBC

PUSH HL E5

[TRACK LOOP] Save current position to stack.

5EBD

CALL 61D6H to get next track entry.

5EC0

JR C,5ECEH 38 0C

If Carry (entry found), JUMP to 5ECEH.

5EC2

CALL 5EE4H CD E4 5E

CALL 5EE4H to process track data.

5EC5

CALL 5578H to set up source drive.

5EC8

CALL 6190H to reset position.

5ECB

POP HL E1

Restore position from stack.

5ECC

JR 5EBCH 18 EE

[LOOP] back to 5EBCH for next track.

5ECEH - Copy Track Entry Data

This routine copies the track entry data to the destination buffer.

5ECE

INC HL 23

Advance past entry marker.

5ECF

LD A,(HL) 7E

Load track number from entry.

5ED0

CALL 56EFH CD EF 56

CALL 56EFH to seek to specified track.

5ED3

LD BC,0018H 01 18 00

Load BC with 0018H (24 bytes) - entry data length.

5ED6

LDIR ED B0

Copy BC bytes from (HL) to (DE).

5ED8

POP HL E1

Restore saved position from stack.

5ED9

SET 4,(HL) CB E6

Set bit 4 of entry marker (processed flag).

5EDB

CALL 5699H to check end condition.

5EDE

JR NZ,5EBCH 20 DC

If NZ FLAG (more data), [LOOP] back to 5EBCH.

5EE0

LD HL,60BFH 21 BF 60

Load HL with address 60BFH (continuation point).

5EE3

PUSH HL E5

Push return address to stack (will return to 60BFH).

5EE4H - Set Up Destination Drive Parameters

This routine sets up the destination drive parameters by reading disk geometry and calculating sector counts.

5EE4

CALL 557DH CD 7D 55

CALL 557DH to select destination drive.

5EE7

CALL 6162H CD 62 61

CALL 6162H to read disk parameters.

5EEA

CALL 6178H CD 78 61

CALL 6178H to calculate sectors per track.

5EED

LD (597DH),A 32 7D 59

Store destination sectors per track to 597DH.

5EF0

LD A,C 79

Load track count from C.

5EF1

LD (59CEH),A 32 CE 59

Store destination track count to 59CEH.

5EF4

LD A,(5997H) 3A 97 59

Load option flags from 5997H.

5EF7

BIT 3,A CB 5F

Test bit 3 (special processing flag).

5EF9

JP Z,5F92H CA 92 5F

If Z FLAG (no special), JUMP to 5F92H.

5EFCH - Special Track Processing Mode

This routine handles special track processing mode for disk copy operations.

5EFC

LD C,00H 0E 00

Load C with 00H (start from track 0).

5EFE

CALL 619DH CD 9D 61

CALL 619DH to initialize track buffer.

5F01

JP NZ,5F89H C2 89 5F

If NZ FLAG (error), JUMP to 5F89H.

5F04

LD (5F1EH),HL 22 1E 5F

Store HL to 5F1EH (self-modifying code location).

5F07

CALL 6190H to reset position.

5F0A

[SCAN LOOP] Check end-of-disk condition.

5F0D

JR Z,5F89H 28 7A

If Z FLAG (end), JUMP to 5F89H.

5F0F

BIT 4,(HL) CB 66

Test bit 4 (processed flag).

5F11

JR Z,5F0AH 28 F7

If Z FLAG (not processed), [LOOP] back to 5F0AH.

5F13

CALL 61D6H to get track entry.

5F16

BIT 5,(HL) CB 6E

Test bit 5 of entry.

5F18

JR NZ,5F0AH 20 F0

If NZ FLAG (skip this), [LOOP] back to 5F0AH.

5F1A

PUSH HL E5

Save position to stack.

5F1B

LD B,05H 06 05

Load B with 05H (loop count).

5F1D

LD HL,0000H 21 00 00

Load HL with 0000H (this location may be modified at 5F1EH).

5F20

PUSH HL E5

Save HL to stack.

5F21

PUSH DE D5

Save DE to stack.

5F22

INC HL 23

[INCREMENT LOOP] Increment HL.

5F23

INC DE 13

Increment DE.

5F24

DJNZ 5F22H 10 FC

Decrement B and [LOOP] if not zero.

5F26

LD B,0BH 06 0B

Load B with 0BH (11) - filename length.

5F28

CALL 6254H CD 54 62

CALL 6254H to compare filenames.

5F2B

POP HL E1

Restore HL from stack.

5F2C

POP DE D1

Restore DE from stack.

5F2D

JR Z,5F32H 28 03

If Z FLAG (match), JUMP to 5F32H.

5F2F

POP HL E1

Restore position from stack.

5F30

JR 5F0AH 18 D8

JUMP back to 5F0AH for next entry.

5F32H - Process Matching File Entry

This routine processes a matching file entry found in the destination directory.

5F32

PUSH DE D5

Save DE to stack.

5F33

PUSH BC C5

Save BC to stack.

5F34

LD BC,0003H 01 03 00

Load BC with 0003H (offset to file attributes).

5F37

ADD HL,BC 09

Add offset to HL (point to attributes).

5F38

EX DE,HL EB

Exchange DE and HL.

5F39

ADD HL,BC 09

Add offset to original pointer.

5F3A

LD A,(DE) 1A

Load source attribute byte.

5F3B

LD (HL),A 77

Store to destination attribute.

5F3C

INC HL 23

Advance HL.

5F3D

PUSH AF F5

Save attribute byte.

5F3E

INC DE 13

Advance DE.

5F3F

LD A,(DE) 1A

Load next source byte.

5F40

LD (HL),A 77

Store to destination.

5F41

LD BC,0010H 01 10 00

Load BC with 0010H (offset to granule info).

5F44

ADD HL,BC 09

Add offset to HL.

5F45

EX DE,HL EB

Exchange DE and HL.

5F46

ADD HL,BC 09

Add offset to original pointer.

5F47

LD A,(HL) 7E

Load source granule info.

5F48

LD (DE),A 12

Store to destination.

5F49

INC DE 13

Advance DE.

5F4A

INC HL 23

Advance HL.

5F4B

LD A,(HL) 7E

Load next source byte.

5F4C

LD (DE),A 12

Store to destination.

5F4D

DEC DE 1B

Move DE back.

5F4E

EX DE,HL EB

Exchange DE and HL.

5F4F

POP AF F1

Restore attribute byte from stack.

5F50

CALL 6209H CD 09 62

CALL 6209H to update directory entry.

5F53

POP BC C1

Restore BC from stack.

5F54

POP DE D1

Restore DE from stack.

5F55

POP HL E1

Restore position from stack.

5F56

SET 5,(HL) CB EE

Set bit 5 of entry marker (completed flag).

5F58

INC HL 23

Advance to track number.

5F59

INC HL 23

Advance past track number.

5F5A

LD (HL),C 71

Store new track value.

5F5B

LD A,C 79

Load track value into A.

5F5C

LD (5B1EH),A 32 1E 5B

Store to 5B1EH (current track variable).

5F5F

CALL 5711H CD 11 57

CALL 5711H to write directory entry.

5F62

LD A,(4317H) 3A 17 43

Load DOS status from 4317H.

5F65

CP 05H FE 05

Compare with 05H (specific status).

5F67

JP NZ,5608H C2 08 56

If NZ FLAG (different status), JUMP to 5608H.

5F6A

INC DE 13

Advance DE to check next byte.

5F6B

LD A,(DE) 1A

Load byte from (DE).

5F6C

BIT 6,A CB 77

Test bit 6 (extended attribute).

5F6E

DEC DE 1B

Move DE back.

5F6F

JR NZ,5F89H 20 18

If NZ FLAG (extended), JUMP to 5F89H.

5F71H - Handle Extended File Attributes

This routine handles files with extended attributes by writing additional directory information.

5F71

LD HL,436BH 21 6B 43

Load HL with address of DOS flag byte at 436BH.

5F74

SET 2,(HL) CB D6

Set bit 2 (enable extended write).

5F76

PUSH HL E5

Save flag address to stack.

5F77

EX DE,HL EB

Exchange DE and HL.

5F78

LD DE,5B17H 11 17 5B

Load DE with address of secondary FCB at 5B17H.

5F7B

CALL 60A9H CD A9 60

CALL 60A9H to write extended data.

5F7E

If NZ FLAG (error), JUMP to 521AH error handler.

5F81

POP HL E1

Restore flag address from stack.

5F82

RES 2,(HL) CB 96

Clear bit 2 (disable extended write).

5F84

LD A,05H 3E 05

Load 05H into A (restore status).

5F86

LD (4317H),A 32 17 43

Store to 4317H (DOS status).

5F89H - Continue Track List Processing

This routine continues processing the track list and loops until all entries are handled.

5F89

LD HL,597DH 21 7D 59

Load HL with address of destination sectors per track.

5F8C

CALL 61BAH CD BA 61

CALL 61BAH to advance sector counter.

5F8F

JP NC,5EFEH D2 FE 5E

If NC (more sectors), JUMP back to 5EFEH.

5F92H - Standard Track Processing

This routine handles standard (non-special) track processing for normal COPY operations.

5F92

LD A,(5995H) 3A 95 59

Load additional option flags from 5995H.

5F95

BIT 3,A CB 5F

Test bit 3 (special mode flag).

5F97

RET NZ C0

If NZ FLAG (special mode), RETURN.

5F98

CALL 56F9H CD F9 56

CALL 56F9H to reset FDC parameters.

5F9B

LD DE,6391H 11 91 63

Load DE with address of directory buffer at 6391H.

5F9E

CALL 6172H CD 72 61

CALL 6172H to set buffer address.

5FA1

CALL 6162H CD 62 61

CALL 6162H to read disk parameters.

5FA4

CALL 6190H to reset track position.

5FA7

[DIRECTORY LOOP] Check end-of-disk condition.

5FAA

JP Z,6092H CA 92 60

If Z FLAG (end), JUMP to 6092H to finish.

5FAD

BIT 4,(HL) CB 66

Test bit 4 (processed flag).

5FAF

JR Z,5FA7H 28 F6

If Z FLAG (not processed), [LOOP] back to 5FA7H.

5FB1

RES 4,(HL) CB A6

Clear bit 4 (processed flag).

5FB3

PUSH HL E5

Save position to stack.

5FB4

BIT 5,(HL) CB 6E

Test bit 5 (completed flag).

5FB6

INC HL 23

Advance past marker byte.

5FB7

JP NZ,6083H C2 83 60

If NZ FLAG (completed), JUMP to 6083H.

5FBA

CALL 61EAH CD EA 61

CALL 61EAH to validate entry.

5FBD

JP NZ,6083H C2 83 60

If NZ FLAG (invalid), JUMP to 6083H.

5FC0

LD A,(HL) 7E

Load track number from entry.

5FC1

LD C,A 4F

Copy track number to C.

5FC2

LD B,00H 06 00

Clear B for 16-bit offset calculation.

5FC4

AND 1FHAND 00011111 E6 1F

Mask with 1FH to get track number (0-31).

5FC6

LD HL,597DH 21 7D 59

Load HL with address of sectors per track.

5FC9

CP (HL) BE

Compare track number with max sectors.

5FCA

JP NC,6083H D2 83 60

If NC (out of range), JUMP to 6083H.

5FCD

LD HL,6291H 21 91 62

Load HL with address of track table at 6291H.

5FD0

ADD HL,BC 09

Add track number as offset.

5FD1

LD A,(HL) 7E

Load track table entry.

5FD2

OR A B7

Test if entry is used.

5FD3

EX DE,HL EB

Exchange DE and HL.

5FD4

JP NZ,6083H C2 83 60

If NZ FLAG (entry used), JUMP to 6083H.

5FD7H - Mark Track Entry and Copy Extent Data

This section executes when an unused track table entry is found. It marks the directory entry as processed, copies the track number into the table, and transfers extent information for file allocation.

5FD7

POP HL E1

Restore HL from stack (points to directory entry marker byte, saved at 5FB3H).

5FD8

SET 5,(HL) CB EE

Set bit 5 (completed flag) in directory entry marker to indicate this entry has been fully processed.

5FDA

PUSH HL E5

Save marker position to stack for later restoration.

5FDB

INC HL 23

Advance past marker byte.

5FDC

INC HL 23

Advance to sector number field in directory entry.

5FDD

LD A,(HL) 7E

Load the original sector number from directory entry.

5FDE

LD (DE),A 12

Store original sector number into track table entry at 6291H+offset (DE points here from 5FD3H).

5FDF

LD A,C 79

Load Register C (contains masked track number 0-31 from 5FC4H) into A.

5FE0

LD (HL),A 77

Store track number into directory entry's sector field (remapping).

5FE1

LD (6028H),A 32 28 60

Self-modifying code: Store track number at 6028H to patch the comparison instruction at 6027H.

5FE4

CALL 56E2H CD E2 56

CALL 56E2H to set up sector buffer address based on track number in A.

5FE7

EX DE,HL EB

Exchange DE and HL. DE now holds directory entry position; HL holds buffer setup result.

5FE8

LD HL,(61D8H) 2A D8 61

Load HL with directory entry pointer from 61D8H (set by 6190H routine).

5FEB

LD BC,0016H 01 16 00

Load BC with 22 bytes (size of file extent record to copy).

5FEE

LDIR ED B0

Block copy 22 bytes from (HL) to (DE), transferring extent allocation data.

5FF0

LD C,(HL) 4E

Load low byte of next extent pointer into C.

5FF1

INC HL 23

Advance to high byte of next extent pointer.

5FF2

LD B,(HL) 46

Load high byte of next extent pointer into B. BC now contains the chain link.

5FF3

PUSH BC C5

Save extent chain pointer to stack.

5FF4

LD B,0AH 06 0A

Load B with 10 (number of granule entries to initialize).

5FF6

LD (6078H),DE ED 53 78 60

Store DE (current buffer position) to 6078H for later reference.

[LOOP START] Initialize 10 granule allocation bytes to FFH (unallocated).

5FFA

LD A,FFH 3E FF

Load A with FFH (unallocated granule marker).

5FFC

LD (DE),A 12

Store FFH to current granule position.

5FFD

INC DE 13

Advance to next granule byte.

5FFE

DJNZ 5FFAH 10 FA

[LOOP] Decrement B and loop until all 10 granule bytes are initialized.

6000

POP BC C1

Restore extent chain pointer from stack.

6001

CALL 5706H CD 06 57

CALL 5706H to process the extent chain and build granule allocation map.

6004

POP HL E1

Restore HL (directory entry marker position from 5FDAH).

6005

BIT 6,(HL) CB 76

Test bit 6 (extended attributes flag) in directory entry.

6007

PUSH HL E5

Save marker position to stack again.

6008

JP Z,6083H CA 83 60

If Z FLAG (no extended attributes), JUMP to 6083H to continue loop.

600BH - Process Extended File Attributes

This section handles files with extended attributes (bit 6 set), calculating granule positions for multi-extent files.

600B

LD A,C 79

Load extent chain low byte into A.

600C

CP FEH FE FE

Compare with FEH (end-of-chain marker). If A equals FEH, Z FLAG set.

600E

JR NC,6083H 30 73

If NC (A >= FEH, meaning end of chain or invalid), JUMP to 6083H.

6010

LD L,A 6F

Load extent chain low byte into L for address calculation.

6011

LD A,(59BCH) 3A BC 59

Load sectors per granule from 59BCH.

6014

CALL 4C92H (SYS0) to calculate H = L * A (granule to sector conversion).

6017

LD A,B 78

Load extent chain high byte into A.

6018

AND 1FHAND 00011111 E6 1F

Mask with 1FH to extract sector offset (bits 0-4).

601A

LD C,A 4F

Store sector offset in C.

601B

LD A,B 78

Reload extent chain high byte.

601C

RLCA 07

Rotate left (shift bits toward high positions).

601D

RLCA 07

Continue rotating.

601E

RLCA 07

Continue rotating (now bits 5-7 are in positions 0-2).

601F

AND 07HAND 00000111 E6 07

Mask with 07H to extract track bits (originally bits 5-7).

6021

LD E,A 5F

Store track offset in E.

6022

LD D,00H 16 00

Clear D for 16-bit addition.

6024

ADD HL,DE 19

Add track offset to granule position.

6025

LD A,02H 3E 02

Load A with 02H (comparison value).

The following instruction at 6027H is self-modified - the immediate value 00H was patched at 5FE1H with the actual sector number.

6027

CP 00H FE 00

Self-modified: Compare A (02H) with patched sector number. The 00H here was set by code at 5FE1H.

6029

JR NZ,6030H 20 05

If NZ FLAG (sector mismatch), JUMP to 6030H for normal calculation.

602B

LD HL,0001H 21 01 00

Load HL with 0001H (special case: first sector).

602E

JR 6064H 18 34

JUMP to 6064H to continue with special case value.

6030H - Calculate Granule Position

This section performs complex calculations to determine the correct granule position within the disk allocation map.

6030

EX DE,HL EB

Exchange DE and HL. DE now holds calculated position.

6031

LD A,(59B7H) 3A B7 59

Load track count from 59B7H.

6034

LD L,A 6F

Store track count in L.

6035

LD A,(59BCH) 3A BC 59

Load sectors per granule from 59BCH.

6038

CALL 4C92H (SYS0) to multiply: H = L * A.

603B

EX DE,HL EB

Exchange back. HL has previous value, DE has multiplication result.

603C

LD A,(59C0H) 3A C0 59

Load granules per lump from 59C0H.

603F

LD B,A 47

Store granules per lump in B for loop counter.

6040

PUSH DE D5

Save multiplication result to stack.

[LOOP START] Increment DE by granules per lump times.

6041

INC DE 13

Increment DE.

6042

DJNZ 6041H 10 FD

[LOOP] Decrement B and loop until granules per lump iterations complete.

6044

OR A B7

Clear carry flag for subtraction.

6045

SBC HL,DE ED 52

Subtract DE from HL (HL = HL - DE).

6047

JR C,6053H 38 0A

If Carry (HL < DE, underflow), JUMP to 6053H for alternate path.

6049

POP DE D1

Restore saved multiplication result.

604A

LD A,(59CEH) 3A CE 59

Load extra sectors count from 59CEH.

604D

LD E,A 5F

Store extra sectors in E.

604E

LD D,00H 16 00

Clear D for 16-bit addition.

6050

ADD HL,DE 19

Add extra sectors to HL.

6051

JR 6058H 18 05

JUMP to 6058H to continue.

6053H - Alternate Granule Calculation Path

This path handles the case where the subtraction resulted in underflow.

6053

ADD HL,DE 19

Add DE back to HL (restore from underflow).

6054

POP DE D1

Restore saved multiplication result from stack.

6055

OR A B7

Clear carry flag.

6056

SBC HL,DE ED 52

Subtract multiplication result from HL.

6058H - Complete Granule Position Calculation

Final steps to calculate the absolute granule position and store it in the allocation map.

6058

EX DE,HL EB

Exchange DE and HL.

6059

LD A,(59C5H) 3A C5 59

Load directory starting lump from 59C5H.

605C

LD L,A 6F

Store starting lump in L.

605D

LD A,(59CAH) 3A CA 59

Load granules per track from 59CAH.

6060

CALL 4C92H (SYS0) to multiply: H = L * A.

6063

ADD HL,DE 19

Add offset in DE to get final granule position.

6064H - Store Granule Allocation Entry

This section stores the calculated granule information into the allocation map and handles overflow conditions.

6064

LD D,C 51

Load sector offset (from 601AH) into D.

6065

LD A,(59CAH) 3A CA 59

Load granules per track from 59CAH.

6068

CALL 4CB4H (SYS0) for division/modulo operation.

606B

INC H 24

Increment H (test for overflow).

606C

DEC H 25

Decrement H back. Z FLAG set if H was 00H (no overflow).

606D

CALL NZ,5240H C4 40 52

If NZ FLAG (overflow detected), CALL 5240H to handle error condition.

6070

LD B,A 47

Store result in B.

6071

RRCA 0F

Rotate A right (divide by 2).

6072

RRCA 0F

Rotate A right again (divide by 4).

6073

RRCA 0F

Rotate A right again (divide by 8, extracting high bits).

6074

PUSH HL E5

Save granule position to stack.

6075

OR D B2

OR with sector offset in D.

6076

LD H,A 67

Store combined value in H.

6077

LD (0000H),HL 22 00 00

Store HL to address 0000H (likely self-modified or placeholder).

607A

LD HL,6391H 21 91 63

Load HL with address of directory buffer at 6391H.

607D

LD C,D 4A

Copy sector offset from D to C.

607E

POP DE D1

Restore granule position from stack into DE.

607F

INC C 0C

Increment C (adjust offset).

6080

CALL 621CH CD 1C 62

CALL 621CH to write granule entry to allocation map.

6083H - Directory Loop Continuation

This is the common exit point for directory loop iterations. It advances to the next entry and loops back to 5FA7H.

6083

CALL 61D6H to get next directory entry parameters.

6086

POP HL E1

Restore HL (directory entry marker position).

6087

BIT 5,(HL) CB 6E

Test bit 5 (completed flag) in directory entry.

6089

JR NZ,608FH 20 04

If NZ FLAG (entry completed), JUMP to 608FH.

608B

LD A,H 7C

Load high byte of HL into A.

608C

LD (60C3H),A 32 C3 60

Self-modifying code: Store H at 60C3H to patch instruction at 60C2H.

608F

JP 5FA7H C3 A7 5F

[LOOP] JUMP back to 5FA7H to process next directory entry.

6092H - Finalize Directory Processing

This routine is called when all directory entries have been processed. It finalizes the track processing and writes allocation data.

6092

CALL 570DH CD 0D 57

CALL 570DH to finalize track processing.

6095

LD HL,6291H 21 91 62

Load HL with address of track allocation table at 6291H.

6098

CALL 616FH CD 6F 61

CALL 616FH to copy 256 bytes from track table to system buffer at 4200H.

609B

PUSH HL E5

Save HL (now points past track table) to stack.

609C

LD A,01H 3E 01

Load A with 01H (sector 1).

609E

CALL 5701H CD 01 57

CALL 5701H to write sector 1 (GAT - Granule Allocation Table).

60A1

POP HL E1

Restore HL from stack.

60A2

CALL 616FH CD 6F 61

CALL 616FH to copy next 256 bytes (HIT - Hash Index Table).

60A5

XOR A AF

Set A to 00H (sector 0).

60A6

JP 5701H C3 01 57

JUMP to 5701H to write sector 0 and return.

60A9H - Write Extended Directory Data

This routine writes extended directory information for files with special attributes. Called from 5F7BH.

60A9

CALL 4980H CD 80 49

CALL 4980H (SYS0) to initialize FCB operation.

60AC

XOR A AF

Set A to 00H.

60AD

LD (4FDBH),A 32 DB 4F

Store 00H to 4FDBH (FCB status flag).

60B0

PUSH HL E5

Save HL (FCB address) to stack.

60B1

INC L 2C

Increment L (advance in FCB).

60B2

INC L 2C

Increment L again.

60B3

INC L 2C

Increment L again (now at offset +3 in FCB).

60B4

LD A,(HL) 7E

Load byte at FCB+3 (file attribute byte).

60B5

LD DE,0011H 11 11 00

Load DE with offset 17 (0011H).

60B8

ADD HL,DE 19

Add 17 to HL (now at FCB+20).

60B9

LD E,(HL) 5E

Load low byte of extent pointer.

60BA

INC HL 23

Advance to high byte.

60BB

LD D,(HL) 56

Load high byte of extent pointer. DE now has extent address.

60BC

JP 4E3DH C3 3D 4E

JUMP to 4E3DH to process extended attributes with DE as extent pointer.

60BFH - Source Directory Scan Entry

This routine initiates scanning of the source disk directory for COPY operations.

60BF

CALL 568BH CD 8B 56

CALL 568BH to flush buffers and prepare for directory scan.

60C2

LD A,00H 3E 00

Self-modified: Load A with patched value (set by code at 608CH). Initial value 00H.

60C4

OR A B7

Test if A is zero.

60C5

JP Z,6157H CA 57 61

If Z FLAG (A = 0, scan complete), JUMP to 6157H to finish.

60C8

CALL 5578H to set up source drive.

60CB

CALL 6190H to reset track position from directory pointers.

[DIRECTORY SCAN LOOP] Scan source directory entries.

60CE

CALL 5699H to get next directory entry.

60D1

JR Z,60F1H 28 1E

If Z FLAG (end of directory), JUMP to 60F1H.

60D3

BIT 5,(HL) CB 6E

Test bit 5 (completed flag) in entry.

60D5

JR NZ,60CEH 20 F7

If NZ FLAG (already completed), [LOOP] skip to next entry.

60D7

CALL 61D6H to get directory entry parameters.

60DA

JR C,60E1H 38 05

If Carry (valid entry found), JUMP to 60E1H.

60DC

CALL 60F5H CD F5 60

CALL 60F5H to process destination directory.

60DF

JR 60C8H 18 E7

[LOOP] Jump back to 60C8H to continue scan.

60E1H - Mark and Copy Source Entry

This section marks a source directory entry as processed and copies its extent data.

60E1

PUSH HL E5

Save directory entry pointer to stack.

60E2

SET 4,(HL) CB E6

Set bit 4 (processed flag) in directory entry.

60E4

INC HL 23

Advance past marker byte.

60E5

LD A,(HL) 7E

Load first data byte (track/sector info).

60E6

CALL 56EFH CD EF 56

CALL 56EFH to initialize sector parameters from A.

60E9

LD BC,0016H 01 16 00

Load BC with 22 bytes (extent record size).

60EC

LDIR ED B0

Block copy 22 bytes of extent data from source to destination buffer.

60EE

POP HL E1

Restore directory entry pointer.

60EF

JR 60CEH 18 DD

[LOOP] Jump back to 60CEH to continue scanning.

60F1H - End of Source Scan - Switch to Destination

This section handles the end of source directory scan and prepares to process the destination.

60F1

LD HL,6157H 21 57 61

Load HL with address 6157H (completion routine).

60F4

PUSH HL E5

Push return address to stack (will return to 6157H when done).

60F5H - Process Destination Directory

This routine scans the destination directory and allocates entries for files being copied.

60F5

CALL 557DH CD 7D 55

CALL 557DH to set up destination drive (primary setup).

60F8

CALL 6190H to reset track position.

[DESTINATION SCAN LOOP]

60FB

CALL 5699H to get next directory entry.

60FE

RET Z C8

If Z FLAG (end of directory), RETURN.

60FF

BIT 4,(HL) CB 66

Test bit 4 (processed flag).

6101

JR Z,60FBH 28 F8

If Z FLAG (not processed), [LOOP] skip to next entry.

6103

PUSH HL E5

Save directory entry pointer.

6104

RES 4,(HL) CB A6

Clear bit 4 (processed flag).

6106

CALL 61D6H to get directory entry parameters.

6109

INC HL 23

Advance past marker byte.

610A

LD B,(HL) 46

Load track number into B.

610B

INC HL 23

Advance to next field.

610C

PUSH DE D5

Save DE to stack.

610D

PUSH HL E5

Save current position to stack.

610E

CALL 50CFH CD CF 50

CALL 50CFH to allocate directory entry on destination.

6111

If NZ FLAG (allocation error), JUMP to 521AH error handler.

6114

EX DE,HL EB

Exchange DE and HL. HL now has allocated entry address.

6115

POP HL E1

Restore source position into HL.

6116

LD (HL),A 77

Store allocation result byte.

6117

POP HL E1

Restore original HL (now has allocated entry from DE).

6118

PUSH DE D5

Save DE (destination entry address) to stack.

6119

LD BC,0016H 01 16 00

Load BC with 22 bytes.

611C

LDIR ED B0

Block copy 22 bytes of extent data to destination entry.

611E

POP DE D1

Restore destination entry address into DE.

611F

CALL 61FCH CD FC 61

CALL 61FCH to check file attributes.

6122

JR Z,614FH 28 2B

If Z FLAG (no special attributes), JUMP to 614FH.

6124

BIT 5,A CB 6F

Test bit 5 (system file flag) in attribute byte.

6126

EX DE,HL EB

Exchange DE and HL.

6127

LD DE,0000H 11 00 00

Load DE with 0000H (default load address).

612A

LD BC,4296H 01 96 42

Load BC with 4296H (default entry point address).

612D

JR Z,613AH 28 0B

If Z FLAG (not system file), JUMP to 613AH with defaults.

612F

LD A,(4044H) 3A 44 40

Load system load address high byte from 4044H.

6132

LD D,A 57

Store in D.

6133

LD A,(4046H) 3A 46 40

Load system entry point high byte from 4046H.

6136

LD E,A 5F

Store in E.

6137

LD BC,5CEFH 01 EF 5C

Load BC with 5CEFH (system file entry point).

613AH - Store File Addresses in Directory Entry

This section stores the load address and entry point in the directory entry for executable files.

613A

INC HL 23

Advance to load address field in directory entry.

613B

LD (HL),E 73

Store low byte of load address.

613C

INC HL 23

Advance to high byte position.

613D

LD (HL),D 72

Store high byte of load address.

613E

INC HL 23

Advance to attribute byte.

613F

LD A,(HL) 7E

Load current attribute byte.

6140

LD DE,000DH 11 0D 00

Load DE with offset 13 to entry point fields.

6143

ADD HL,DE 19

Add offset to reach entry point location.

6144

LD (HL),C 71

Store low byte of entry point.

6145

INC HL 23

Advance to high byte.

6146

LD (HL),B 70

Store high byte of entry point.

6147

INC HL 23

Advance to next field.

6148

LD (HL),C 71

Store low byte again (duplicate for compatibility).

6149

INC HL 23

Advance.

614A

LD (HL),B 70

Store high byte again.

614B

INC HL 23

Advance to next section.

614C

CALL 6209H CD 09 62

CALL 6209H to finalize directory entry attributes.

614FH - Write Directory Entry and Continue

This section writes the completed directory entry and continues processing.

614F

CALL 5711H CD 11 57

CALL 5711H to write directory entry to disk.

6152

POP HL E1

Restore directory scan position from stack.

6153

SET 5,(HL) CB EE

Set bit 5 (completed flag) in entry.

6155

JR 60FBH 18 A4

[LOOP] Jump back to 60FBH to continue destination scan.

6157H - Complete COPY Operation

This routine marks the COPY operation as complete and returns to the main DOS handler.

6157

LD A,FFH 3E FF

Load A with FFH (completion marker).

6159

LD (5B1EH),A 32 1E 5B

Store FFH to 5B1EH (copy complete flag).

615C

LD (586AH),A 32 6A 58

Store FFH to 586AH (secondary complete flag).

615F

JP 524EH C3 4E 52

JUMP to 524EH to return to DOS with success.

6162H - Read Disk Parameters

This routine reads disk parameters and sets up the track allocation table buffer.

6162

LD A,01H 3E 01

Load A with 01H (sector 1 - GAT sector).

6164

CALL 56FAH CD FA 56

CALL 56FAH to read sector 1 into buffer.

6167

LD DE,6291H 11 91 62

Load DE with address of track allocation table at 6291H.

616A

CALL 6172H CD 72 61

CALL 6172H to copy 256 bytes from system buffer to track table.

616D

DEC H 25

Decrement H (adjust buffer pointer).

616E

RET C9

RETURN to caller.

616FH - Copy 256 Bytes to System Buffer

This utility routine copies 256 bytes from HL to the system buffer at 4200H.

616F

LD DE,4200H 11 00 42

Load DE with 4200H (system sector buffer address).

6172H - Block Copy 256 Bytes

General purpose 256-byte block copy routine. Entry: HL=source, DE=destination.

6172

LD BC,0100H 01 00 01

Load BC with 256 (0100H) bytes to copy.

6175

LDIR ED B0

Block copy 256 bytes from (HL) to (DE).

6177

RET C9

RETURN to caller. HL and DE now point past copied data.

6178H - Calculate Directory Sector Parameters

This routine calculates sector parameters based on directory configuration.

6178

CALL 61F6H to check double-density mode flag.

617B

LD A,10H 3E 10

Load A with 16 (10H) - default sectors for single density.

617D

LD C,06H 0E 06

Load C with 6 - default value.

617F

RET NZ C0

If NZ FLAG (single density), RETURN with defaults.

6180

LD E,05H 1E 05

Load E with 5 (sectors per granule for DD).

6182

LD A,(421FH) 3A 1F 42

Load A from 421FH (disk parameter byte).

6185

ADD 08H C6 08

Add 8 to disk parameter.

6187

LD B,A 47

Store result in B.

6188

LD C,00H 0E 00

Initialize C to 0.

[LOOP START] Calculate granule count by repeated subtraction.

618A

INC C 0C

Increment granule counter.

618B

SUB E 93

Subtract sectors per granule from A.

618C

JR NC,618AH 30 FC

[LOOP] If NC (not underflow), continue counting.

618E

LD A,B 78

Restore original parameter to A.

618F

RET C9

RETURN with A=parameter, C=granule count.

6190H - Reset Track Position from Directory Pointers

This routine initializes the directory scan position from system pointers at 5D12H-5D14H.

6190

LD HL,(5D14H) 2A 14 5D

Load HL with directory entry pointer from 5D14H.

6193

LD (61D8H),HL 22 D8 61

Store to 61D8H (working directory pointer).

6196

LD HL,(5D12H) 2A 12 5D

Load HL with directory buffer end from 5D12H.

6199

DEC HL 2B

Decrement HL (adjust for entry size).

619A

DEC HL 2B

Decrement again.

619B

DEC HL 2B

Decrement again (back up 3 bytes).

619C

RET C9

RETURN with HL pointing to adjusted position.

619DH - Track Table Lookup

This routine looks up a track entry in the allocation table at 6291H and validates it.

619D

LD B,00H 06 00

Clear B for 16-bit index (BC will be the offset).

619F

LD HL,6291H 21 91 62

Load HL with base address of track allocation table at 6291H.

61A2

ADD HL,BC 09

Add offset in BC to get address of specific track entry.

61A3

LD A,(HL) 7E

Load track table entry value into A.

61A4

CP 01H FE 01

Compare with 01H. If A < 1, Carry is set (entry is 00H/unused).

61A6

LD B,A 47

Copy track entry value to B for later use.

61A7

RET C D8

If Carry (entry < 1, meaning unused), RETURN early.

61A8

CALL 61F6H to check double-density mode flag.

61AB

LD A,C 79

Load sector counter from C into A.

61AC

JR NZ,61B1H 20 03

If NZ FLAG (single density mode), JUMP to 61B1H.

61AE

CP 02H FE 02

Compare sector counter with 02H.

61B0

RET C D8

If Carry (sector < 2), RETURN (skip system sectors in DD mode).

61B1

CALL 56E2H CD E2 56

CALL 56E2H to set up sector buffer from track number.

61B4

LD A,(HL) 7E

Load byte from sector buffer.

61B5

AND 90H E6 90

Mask with 90H (bits 7 and 4 - status flags).

61B7

CP 10H FE 10

Compare with 10H. Z FLAG set if only bit 4 is set.

61B9

RET C9

RETURN with Z FLAG indicating status (Z=valid entry).

61BAH - Advance Sector Counter

This routine advances the sector counter and checks if we've reached the end of the track. Returns Carry if track is complete.

61BA

CALL 61F6H to check double-density mode flag.

61BD

LD A,50H 3E 50

Load A with 80 (50H) - sectors per track for single density.

61BF

JR NZ,61C7H 20 06

If NZ FLAG (single density), JUMP to 61C7H with A=50H.

61C1

LD A,C 79

Load current sector counter from C.

61C2

ADD 20H C6 20

Add 32 (20H) to sector counter (double-density increment).

61C4

LD C,A 4F

Store updated counter back to C.

61C5

RET NC D0

If NC (no overflow), RETURN - more sectors to process.

61C6

LD A,(HL) 7E

Load sectors per track from (HL) on overflow.

61C7

DEC A 3D

Decrement sectors per track (convert to max index).

61C8

INC C 0C

Increment sector counter.

61C9

CP C B9

Compare max sector with counter. Carry set if C > A (track complete).

61CA

RET C9

RETURN with Carry indicating track complete status.

61CBH - Granule Boundary Calculation

This routine calculates granule boundaries by repeated subtraction, storing intermediate values.

61CB

CP B B8

Compare A with B (granule count vs limit).

61CC

RET C D8

If Carry (A < B), RETURN - boundary reached.

61CD

LD (HL),2FH 36 2F

Store 2FH (ASCII '/') as delimiter marker at (HL).

[LOOP START] Increment marker and subtract until underflow.

61CF

INC (HL) 34

Increment value at (HL) (converts '/' to '0', then '1', etc.).

61D0

SUB B 90

Subtract B from A.

61D1

JR NC,61CFH 30 FC

[LOOP] If NC (no underflow), continue incrementing.

61D3

ADD A,B 80

Add B back to restore remainder after underflow.

61D4

INC HL 23

Advance to next position.

61D5

RET C9

RETURN with A=remainder, HL=next position.

61D6H - Get Directory Entry Parameters

This routine retrieves directory entry parameters using RST 18H (DOS function call) and calculates the entry pointer.

61D6

PUSH HL E5

Save HL to stack.

61D7

LD HL,0000H 21 00 00

Load HL with 0000H (parameter for RST call).

61DA

LD DE,0000H 11 00 00

Load DE with 0000H (secondary parameter).

61DD

RST 18H DF

Call RST 18H - DOS function dispatcher. Returns directory info.

61DE

PUSH AF F5

Save flags and result to stack.

61DF

EX DE,HL EB

Exchange DE and HL. HL now has result from RST 18H.

61E0

LD HL,0018H 21 18 00

Load HL with 24 (0018H) - size of directory entry.

61E3

ADD HL,DE 19

Add base address from DE to get next entry pointer.

61E4

LD (61D8H),HL 22 D8 61

Store calculated pointer to 61D8H (working directory pointer).

61E7

POP AF F1

Restore flags and result.

61E8

POP HL E1

Restore original HL.

61E9

RET C9

RETURN to caller.

61EAH - Validate Directory Entry

This routine validates a directory entry by checking attribute flags. Returns Z if entry is valid for processing.

61EA

PUSH HL E5

Save HL to stack.

61EB

LD HL,59C7H 21 C7 59

Load HL with address of file attribute mask at 59C7H.

61EE

LD A,(59B9H) 3A B9 59

Load current file attributes from 59B9H.

61F1

OR (HL) B6

OR with attribute mask at (HL).

61F2

POP HL E1

Restore HL.

61F3

AND 20HAND 00100000 E6 20

Mask with 20H (bit 5 - system file flag). Z if not system file.

61F5

RET C9

RETURN with Z FLAG indicating validity (Z=valid for copy).

61F6H - Check Double-Density Mode Flag

This routine checks if the disk is operating in double-density mode by examining bit 5 of the drive configuration byte.

61F6

LD A,(430CH) 3A 0C 43

Load drive configuration byte from 430CH.

61F9

AND 20HAND 00100000 E6 20

Mask with 20H (bit 5 - double-density flag). Z if single density.

61FB

RET C9

RETURN with Z FLAG indicating density (Z=single, NZ=double).

61FCH - Check File Attributes

This routine checks file attributes for special handling requirements during copy operations.

61FC

PUSH HL E5

Save HL to stack.

61FD

LD HL,59C7H 21 C7 59

Load HL with address of file attribute mask at 59C7H.

6200

LD A,(59B9H) 3A B9 59

Load current file attributes from 59B9H.

6203

XOR (HL) AE

XOR with attribute mask (find differences).

6204

AND 20HAND 00100000 E6 20

Mask with 20H (bit 5). Z if attributes match for bit 5.

6206

LD A,(HL) 7E

Load attribute mask value into A.

6207

POP HL E1

Restore HL.

6208

RET C9

RETURN with Z FLAG and A=attribute mask.

6209H - Finalize Directory Entry Attributes

This routine finalizes directory entry attributes, adjusting load/entry addresses based on file type.

6209

OR A B7

Test A (attribute byte). Sets flags based on value.

620A

CALL NZ,61FCH C4 FC 61

If NZ (has attributes), CALL 61FCH to check file attributes.

620D

RET Z C8

If Z FLAG (no special handling needed), RETURN.

620E

LD E,(HL) 5E

Load low byte of address field.

620F

INC HL 23

Advance to high byte.

6210

LD D,(HL) 56

Load high byte. DE now has address value.

6211

INC DE 13

Increment address by 1.

6212

BIT 5,A CB 6F

Test bit 5 (system file flag) in attribute byte.

6214

JR Z,6218H 28 02

If Z FLAG (not system file), JUMP to 6218H.

6216

DEC DE 1B

Decrement DE (undo increment).

6217

DEC DE 1B

Decrement again (net -1 from original).

6218

LD (HL),D 72

Store adjusted high byte back.

6219

DEC HL 2B

Move back to low byte position.

621A

LD (HL),E 73

Store adjusted low byte.

621B

RET C9

RETURN to caller.

621CH - Write Granule Entry to Allocation Map

This routine writes a granule allocation entry to the GAT (Granule Allocation Table). It sets the appropriate bit in the allocation bitmap.

621C

LD D,00H 16 00

Clear D for 16-bit offset calculation.

621E

ADD HL,DE 19

Add offset E to HL (base address of allocation table).

621F

LD D,80H 16 80

Load D with 80H (bit 7 mask - starting bit position).

6221

LD A,B 78

Load granule bit position from B.

6222

INC B 04

Increment B for loop counter.

[LOOP START] Rotate bit mask to correct position.

6223

RLC D CB 02

Rotate D left (shift bit mask).

6225

DJNZ 6223H 10 FC

[LOOP] Decrement B and loop until bit is in position.

6227

LD B,A 47

Restore original bit position to B.

6228

LD A,(59CAH) 3A CA 59

Load granules per track from 59CAH.

622B

SUB B 90

Subtract bit position from granules per track.

622C

LD B,A 47

Store remaining count in B.

622D

PUSH HL E5

Save current allocation table position.

622E

LD HL,59C6H 21 C6 59

Load HL with address of granule limit at 59C6H.

6231

LD A,E 7B

Load current byte offset into A.

6232

CP (HL) BE

Compare with granule limit.

6233

POP HL E1

Restore allocation table position.

6234

JR NC,6249H 30 13

If NC (offset >= limit), JUMP to 6249H error handler.

6236

LD A,(HL) 7E

Load current allocation byte.

6237

AND D A2

AND with bit mask to test if granule already allocated.

6238

JR NZ,6249H 20 0F

If NZ (already allocated), JUMP to 6249H error handler.

623A

LD A,(HL) 7E

Load current allocation byte again.

623B

OR D B2

OR with bit mask to set the granule bit.

623C

LD (HL),A 77

Store updated allocation byte.

623D

DEC C 0D

Decrement granule counter.

623E

RET Z C8

If Z FLAG (all granules processed), RETURN.

623F

RLC D CB 02

Rotate bit mask left for next granule.

6241

DJNZ 622DH 10 EA

[LOOP] Decrement B and loop if more bits in this byte.

6243

LD D,01H 16 01

Reset bit mask to 01H (bit 0) for next byte.

6245

INC HL 23

Advance to next allocation byte.

6246

INC E 1C

Increment byte offset counter.

6247

JR 6228H 18 DF

[LOOP] Jump back to 6228H to continue processing.

6249H - Granule Allocation Error

This routine handles errors during granule allocation (overflow or duplicate allocation).

6249

CALL 5240H CD 40 52

CALL 5240H to handle allocation error.

624CH - Message Strings and Response Table (DATA)

This section contains ASCII message strings used for COPY command prompts and status messages. The strings are terminated with 03H (ETX).

624C

DEFB 20H,20H 20 20

Two space characters (padding).

624E

DEFB 20H,11H 20 11

Space + 11H (Device Control 1).

6250

DEFB D0H D0

High-bit character (possibly cursor control).

6251

DEFB 42H 42

ASCII B.

6252

DEFB 06H,08H 06 08

Control characters.

6254

DEFB 1AH 1A

1AH (Substitute/EOF marker).

6255

DEFB BEH BE

High-bit character.

6256

DEFB C0H C0

High-bit character.

6257

DEFB 13H 13

13H (XOFF/Device Control 3).

6258

DEFB 23H 23

ASCII #.

6259

DEFB 10H,F9H 10 F9

Control + high-bit character.

625B

DEFB C9H C9

High-bit character (or RET opcode if executed).

625C

DEFM "RQNY" 52 51 4E 59

Response key table: R=Restart, Q=Quit, N=No, Y=Yes.

6260

DEFB 00H 00

NUL terminator for response table.

6261

DEFM " COPY IT? (Y/N/R/Q) " 20 20 20 20 43 4F 50 59 20 49 54 3F 20 20 28 59 2F 4E 2F 52 2F 51 29 20 20

Prompt message for CFWO (Check File With Operator) option.

627A

DEFB 03H 03

ETX (End of Text) - string terminator.

627B

DEFM "COPYING" 43 4F 50 59 49 4E 47

Status message displayed during copy operation.

6282

DEFB 03H 03

ETX - string terminator.

6283

DEFM "ILF/XLF FILE " 49 4C 46 2F 58 4C 46 20 46 49 4C 45 20

Message for Include List File / Exclude List File operations.

6290

DEFB 03H 03

ETX - string terminator.

6291H - Main COPY/FORMAT Processing Entry

This is a major entry point for COPY/FORMAT processing. It checks option flags and sets up file operations. Note: Address 6291H is also used as the base of the track allocation table (256 bytes) - this code executes from a different context.

6291

LD A,(5997H) 3A 97 59

Load option flags byte 4 from 5997H.

6294

AND 30H E6 30

Mask with 30H (bits 4-5: ILF/XLF flags).

6296

LD HL,4200H 21 00 42

Load HL with system sector buffer at 4200H.

6299

LD DE,4480H 11 80 44

Load DE with secondary buffer at 4480H.

629C

CALL NZ,4424H C4 24 44

If NZ (ILF or XLF active), CALL 4424H (SYS0) to open list file.

629F

JP NZ,5D67H C2 67 5D

If NZ FLAG (open failed), JUMP to 5D67H error handler.

62A2

LD A,(5996H) 3A 96 59

Load option flags byte 3 from 5996H.

62A5

AND 08HAND 00001000 E6 08

Mask with 08H (bit 3: special mode flag).

62A7

LD A,F3H 3E F3

Load A with F3H (default sector read mask).

62A9

JR Z,62ADH 28 02

If Z FLAG (normal mode), JUMP to 62ADH.

62AB

LD A,E5H 3E E5

Load A with E5H (special mode sector mask - deleted data mark).

62AD

CALL 568DH to initialize sector handling with mask in A.

62B0H - Initialize Source Drive and Check Options

This section initializes the source drive and checks various COPY option flags to determine the operation mode.

62B0

CALL 5578H to set up source drive.

62B3

LD A,(436CH) 3A 6C 43

Load drive status byte from 436CH.

62B6

AND 82H E6 82

Mask with 82H (bits 7 and 1 - density and side flags).

62B8

CP 80H FE 80

Compare with 80H. Z if only bit 7 set (single-sided DD).

62BA

JR Z,62C3H 28 07

If Z FLAG (single-sided DD), JUMP to 62C3H.

62BC

LD A,(5994H) 3A 94 59

Load option flags byte 1 from 5994H.

62BF

AND 02H E6 02

Mask with 02H (bit 1 - bypass directory update flag).

62C1

JR NZ,632CH 20 69

If NZ FLAG (BDU option set), JUMP to 632CH.

62C3

CALL 56F9H CD F9 56

CALL 56F9H to reset FDC parameters.

62C6

LD A,(5995H) 3A 95 59

Load option flags byte 2 from 5995H.

62C9

BIT 5,A CB 6F

Test bit 5 (keep destination date flag - KDD).

62CB

JR NZ,62D3H 20 06

If NZ FLAG (KDD set), JUMP to 62D3H - skip date copy.

62CD

LD HL,(42CEH) 2A CE 42

Load source disk date from 42CEH (sector buffer offset).

62D0

LD (5981H),HL 22 81 59

Store to 5981H (destination date buffer).

62D3

LD A,(5994H) 3A 94 59

Load option flags byte 1 from 5994H.

62D6

BIT 2,A CB 57

Test bit 2 (keep destination name flag - KDN).

62D8

JR NZ,62E5H 20 0B

If NZ FLAG (KDN set), JUMP to 62E5H - skip name copy.

62DA

LD HL,42D0H 21 D0 42

Load HL with source disk name address at 42D0H.

62DD

LD DE,5983H 11 83 59

Load DE with destination name buffer at 5983H.

62E0

LD BC,0008H 01 08 00

Load BC with 8 (disk name length).

62E3

LDIR ED B0

Block copy 8 bytes (disk name from source to destination buffer).

62E5

LD A,(5995H) 3A 95 59

Load option flags byte 2 from 5995H.

62E8

BIT 4,A CB 67

Test bit 4 (use source date flag - USD).

62EA

JR Z,62F7H 28 0B

If Z FLAG (USD not set), JUMP to 62F7H.

62EC

LD HL,42D8H 21 D8 42

Load HL with source disk date string at 42D8H.

62EF

LD DE,598BH 11 8B 59

Load DE with destination date string buffer at 598BH.

62F2

LD BC,0008H 01 08 00

Load BC with 8 (date string length).

62F5

LDIR ED B0

Block copy 8 bytes (date string from source to destination).

62F7

LD A,(5996H) 3A 96 59

Load option flags byte 3 from 5996H.

62FA

BIT 7,A CB 7F

Test bit 7 (source name check flag - SN option).

62FC

JR Z,6314H 28 16

If Z FLAG (SN not set), JUMP to 6314H.

62FE

LD HL,5968H 21 68 59

Load HL with address of expected source name at 5968H.

6301

CALL 624FH CD 4F 62

CALL 624FH to compare source name with expected.

6304

JR Z,632CH 28 26

If Z FLAG (names match), JUMP to 632CH to continue.

6306

LD HL,5A3CH 21 3C 5A

Load HL with address of mismatch message buffer at 5A3CH.

6309

CALL 692FH CD 2F 69

CALL 692FH to format mismatch message.

630C

CALL 693BH CD 3B 69

CALL 693BH to display name mismatch prompt.

630F

CALL 58C8H CD C8 58

CALL 58C8H to get operator response (Y/N).

6312

JR NZ,62C3H 20 AF

If NZ FLAG (operator said No), [LOOP] back to 62C3H to retry.

6314H - Validate Disk Geometry Match

This section validates that source and destination disk geometries are compatible.

6314

LD A,(436CH) 3A 6C 43

Load drive status byte from 436CH.

6317

AND 82H E6 82

Mask with 82H (density and side flags).

6319

CP 80H FE 80

Compare with 80H.

631B

JR NZ,632CH 20 0F

If NZ FLAG (not single-sided DD), JUMP to 632CH.

631D

LD HL,(42CEH) 2A CE 42

Load source disk parameters from 42CEH.

6320

LD DE,(5978H) ED 5B 78 59

Load destination disk parameters from 5978H.

6324

OR A B7

Clear Carry for subtraction.

6325

SBC HL,DE ED 52

Subtract destination from source parameters.

6327

LD A,37H 3E 37

Load A with error code 37H (geometry mismatch).

6329

If NZ FLAG (parameters don't match), JUMP to 521AH error handler.

632CH - Continue COPY Setup

This section continues COPY setup after option validation, clearing flags and checking for special modes.

632C

LD HL,5996H 21 96 59

Load HL with address of option flags byte 3 at 5996H.

632F

RES 7,(HL) CB BE

Clear bit 7 (source name check flag - no longer needed).

6331

LD A,(5996H) 3A 96 59

Load option flags byte 3 into A.

6334

BIT 3,A CB 5F

Test bit 3 (CBF - Copy By File mode).

6336

JP NZ,5D16H C2 16 5D

If NZ FLAG (CBF mode), JUMP to 5D16H for file-by-file copy.

6339

LD HL,(59D1H) 2A D1 59

Load source track count from 59D1H.

633C

LD DE,(59C3H) ED 5B C3 59

Load destination track count from 59C3H.

6340

RST 18H DF

Call RST 18H - DOS function to compare track counts.

6341

LD A,(5994H) 3A 94 59

Load option flags byte 1 into A.

6344

LD C,A 4F

Copy flags to C for bit testing.

6345

LD HL,(59C1H) 2A C1 59

Load first track allocation value from 59C1H.

6348

JR NC,6352H 30 08

If NC (source <= destination), JUMP to 6352H.

634A

BIT 1,C CB 49

Test bit 1 (BDU - Bypass Directory Update flag).

634C

JP Z,5204H CA 04 52

If Z FLAG (BDU not set and source > dest), JUMP to 5204H - disk too small error.

634F

LD HL,(59CFH) 2A CF 59

Load alternate allocation value from 59CFH.

6352

LD (5AF1H),HL 22 F1 5A

Store allocation value to 5AF1H.

6355

NOP 00

No operation (placeholder/alignment).

6356

NOP 00

No operation (placeholder/alignment).

6357

BIT 1,C CB 49

Test bit 1 (BDU flag) again.

6359

JR NZ,6365H 20 0A

If NZ FLAG (BDU set), JUMP to 6365H - skip granule check.

635B

LD HL,59CAH 21 CA 59

Load HL with address of granules per track at 59CAH.

635E

LD A,(59BCH) 3A BC 59

Load sectors per granule from 59BCH.

6361

CP (HL) BE

Compare with granules per track.

6362

JP NZ,5204H C2 04 52

If NZ FLAG (granule size mismatch), JUMP to 5204H error.

6365

CALL 674DH CD 4D 67

CALL 674DH to initialize track buffers.

6368

CALL 67C3H CD C3 67

CALL 67C3H to set up copy parameters.

636B

LD HL,0000H 21 00 00

Load HL with 0000H.

636E

LD (5AEFH),HL 22 EF 5A

Store 0000H to 5AEFH (sector counter).

6371

LD (5B21H),HL 22 21 5B

Store 0000H to 5B21H (track counter).

6374

JP 5273H C3 73 52

JUMP to 5273H to begin main copy loop.

6377H - Two-Drive Copy Initialization

This routine initializes parameters for copying between two different drives.

6377

LD BC,594CH 01 4C 59

Load BC with address of source drive number at 594CH.

637A

LD DE,5AE5H 11 E5 5A

Load DE with address of source filespec buffer at 5AE5H.

637D

CALL 6437H CD 37 64

CALL 6437H to set up source drive parameters.

6380

LD BC,5956H 01 56 59

Load BC with address of destination drive number at 5956H.

6383

LD DE,5B17H 11 17 5B

Load DE with address of destination filespec buffer at 5B17H.

6386

CALL 6437H CD 37 64

CALL 6437H to set up destination drive parameters.

6389

CALL 5C96H CD 96 5C

CALL 5C96H to initialize sector size parameters.

638C

CALL 568BH CD 8B 56

CALL 568BH to flush buffers.

638F

JP 5279H C3 79 52

JUMP to 5279H to continue copy operation.

6392H - Parse Destination Drive Number

This routine parses and validates the destination drive number from the command line.

6392

CALL 6ECBH CD CB 6E

CALL 6ECBH to skip whitespace and get next character.

6395

RET NC D0

If NC (no valid drive number found), RETURN.

6396

LD (5B1DH),A 32 1D 5B

Store drive number to 5B1DH.

6399

LD (5956H),A 32 56 59

Store to destination drive number at 5956H.

639C

LD (4DFAH),A 32 FA 4D

Store to 4DFAH (self-modifying code location).

639F

RET C9

RETURN to caller.

63A0H - Parse Track Count Parameter

This routine parses track count parameter from command line (e.g., "=40" or "=80").

63A0

LD DE,64A9H 11 A9 64

Load DE with address of track count storage at 64A9H.

63A3

LD A,(HL) 7E

Load current character from command line.

63A4

CP 3DH FE 3D

Compare with = (3DH) character.

63A6

RET NZ C0

If NZ FLAG (not '='), RETURN - no track count specified.

63A7

PUSH DE D5

Save storage address to stack.

63A8

INC HL 23

Advance past '=' character.

63A9

CALL 6EE7H CD E7 6E

CALL 6EE7H to parse decimal number.

63AC

POP DE D1

Restore storage address.

63AD

OR A B7

Test if parsed number is zero.

63AE

LD (DE),A 12

Store track count to (DE).

63AF

RET NZ C0

If NZ FLAG (valid non-zero count), RETURN.

63B0

JP 5218H C3 18 52

JUMP to 5218H - invalid parameter error.

63B3H - Flush Drives and Initialize Parameters

This routine flushes both source and destination drives and loads disk parameters into working storage.

63B3

LD B,03H 06 03

Load B with 03H (flush mode for all drives).

63B5

CALL 5646H CD 46 56

CALL 5646H to flush all drive buffers.

63B8

LD B,02H 06 02

Load B with 02H (flush destination only).

63BA

LD HL,593BH 21 3B 59

Load HL with address of drive status flags at 593BH.

63BD

SET 7,(HL) CB FE

Set bit 7 (drive needs flush flag).

63BF

CALL 5646H CD 46 56

CALL 5646H to flush destination drive.

63C2

LD BC,(594CH) ED 4B 4C 59

Load BC with source drive number from 594CH (B=high, C=low).

63C6

LD HL,59B7H 21 B7 59

Load HL with address of source parameters buffer at 59B7H.

63C9

LD A,FFH 3E FF

Load A with FFH (default/all tracks).

63CB

CALL 63ECH CD EC 63

CALL 63ECH to load source drive parameters.

63CE

LD BC,(5956H) ED 4B 56 59

Load BC with destination drive number from 5956H.

63D2

LD HL,59C5H 21 C5 59

Load HL with address of destination parameters buffer at 59C5H.

63D5

LD A,FFH 3E FF

Load A with FFH.

63D7

CALL 63ECH CD EC 63

CALL 63ECH to load destination drive parameters.

63DA

LD HL,64A3H 21 A3 64

Load HL with address of parameter override table at 64A3H.

63DD

LD C,(HL) 4E

Load count of override entries into C.

63DE

INC HL 23

Advance to first entry's address low byte.

[LOOP START] Apply parameter overrides from table.

63DF

LD E,(HL) 5E

Load low byte of target address.

63E0

INC HL 23

Advance to high byte.

63E1

LD D,(HL) 56

Load high byte. DE now has target address.

63E2

INC HL 23

Advance to override value.

63E3

LD A,(HL) 7E

Load override value.

63E4

OR A B7

Test if value is zero (skip marker).

63E5

JR Z,63E8H 28 01

If Z FLAG (zero = skip), JUMP to 63E8H.

63E7

LD (DE),A 12

Store override value to target address.

63E8

DEC C 0D

Decrement entry counter.

63E9

JR NZ,63DEH 20 F3

[LOOP] If NZ (more entries), continue loop.

63EB

RET C9

RETURN to caller.

63ECH - Load Drive Parameters

This routine loads drive parameters from PDRIVE table into working storage. Entry: A=track count (FFH=use default), BC=drive info, HL=destination buffer.

63EC

CP FFH FE FF

Compare A with FFH (default marker).

63EE

RET Z C8

If Z FLAG (use default), RETURN without changes.

63EF

RLCA 07

Rotate A left (multiply by 2).

63F0

RLCA 07

Rotate again (multiply by 4).

63F1

RLCA 07

Rotate again (multiply by 8).

63F2

RLCA 07

Rotate again (multiply by 16 - PDRIVE entry size offset).

63F3

PUSH HL E5

Save destination buffer address.

63F4

LD HL,5940H 21 40 59

Load HL with drive flags buffer at 5940H.

63F7

PUSH AF F5

Save calculated offset.

63F8

LD A,C 79

Load drive number low byte into A.

63F9

OR A B7

Test if drive number is zero (source drive).

63FA

JR NZ,6406H 20 0A

If NZ FLAG (not source), JUMP to 6406H.

63FC

DEC A 3D

Decrement A (now FFH).

63FD

XOR B A8

XOR with B (drive number high byte).

63FE

INC HL 23

Advance to second flag byte at 5941H.

63FF

AND (HL) A6

AND with flag byte to mask relevant bits.

6400

LD (HL),A 77

Store masked result back to flag byte.

6401

DEC HL 2B

Move back to first flag byte at 5940H.

6402

INC B 04

Increment B (drive number high byte).

6403

LD A,(HL) 7E

Load first flag byte.

6404

OR B B0

OR with incremented drive number.

6405

LD (HL),A 77

Store updated flag byte.

6406

LD A,(5956H) 3A 56 59

Load destination drive number from 5956H.

6409

LD B,A 47

Copy to B for comparison.

640A

LD A,(594CH) 3A 4C 59

Load source drive number from 594CH.

640D

CP B B8

Compare source with destination drive.

640E

JR NZ,6417H 20 07

If NZ FLAG (different drives), JUMP to 6417H.

Same drive for source and destination - set single-drive copy mode flags.

6410

LD A,(HL) 7E

Load flag byte.

6411

OR 06H F6 06

OR with 06H (bits 1-2: single-drive copy mode flags).

6413

LD (HL),A 77

Store updated flags.

6414

INC HL 23

Advance to second flag byte.

6415

LD (HL),01H 36 01

Store 01H (single-drive indicator).

6417

CALL 6424H CD 24 64

CALL 6424H to read PDRIVE table from disk.

641A

POP AF F1

Restore calculated offset into A.

641B

ADD A,L 85

Add offset to L (pointing into PDRIVE table).

641C

LD L,A 6F

Store result back to L. HL now points to specific PDRIVE entry.

641D

POP DE D1

Restore destination buffer address into DE.

641E

LD BC,000AH 01 0A 00

Load BC with 10 (PDRIVE entry size to copy).

6421

LDIR ED B0

Block copy 10 bytes from PDRIVE entry to destination buffer.

6423

RET C9

RETURN to caller.

6424H - Read PDRIVE Table from Disk

Reads the PDRIVE configuration sector (sector 2) from disk into the system buffer at 4200H. Called from 6417H during drive parameter initialization.

6424

LD HL,0002H 21 02 00

Load HL with 2 (PDRIVE sector number).

6427

LD (5B53H),HL 22 53 5B

Store sector number at 5B53H (sector parameter).

642A

LD HL,4200H 21 00 42

Load HL with 4200H (system buffer address).

642D

LD DE,5B49H 11 49 5B

Load DE with 5B49H (FCB address for sector read).

6430

CALL 4436H CD 36 44

CALL 4436H (SYS0) to read sector into buffer.

6433

RET Z C8

If Z FLAG (read successful), RETURN.

6434

JUMP to 521AH error handler on read failure.

6437H - Parse Drive Specification

Parses drive specification from command line. Handles "d:" format for drive numbers 0-5. Entry: DE=command line pointer, HL=5940H (drive flags), BC=parameter storage. Returns drive number or handles filespec parsing.

6437

LD HL,5940H 21 40 59

Load HL with 5940H (drive flags buffer).

643A

LD A,(DE) 1A

Load character from command line.

643B

CP 3AH FE 3A

Compare with ':' (colon - drive separator).

643D

INC DE 13

Advance command line pointer.

643E

JR NZ,6458H 20 18

If NZ FLAG (not colon), JUMP to 6458H check for ETX.

6440

LD A,(HL) 7E

Load current drive count from flags.

6441

CP 06H FE 06

Compare with 6 (max drive number + 1).

6443

JR NC,6482H 30 3D

If NC FLAG (6 or more drives), JUMP to 6482H error.

6445

PUSH HL E5

Save drive flags pointer.

6446

PUSH BC C5

Save parameter storage pointer.

6447

EX DE,HL EB

HL = command line pointer.

6448

CALL 6ED7H CD D7 6E

CALL 6ED7H to parse drive number from command line.

644B

POP BC C1

Restore parameter storage pointer.

644C

POP HL E1

Restore drive flags pointer.

644D

OR A B7

Test if parse succeeded (A=0 on success).

644E

LD (BC),A 02

Store result at (BC).

644F

RET NZ C0

If NZ FLAG (parse failed), RETURN with error.

6450

INC BC 03

Advance to next parameter byte.

6451

LD A,(BC) 0A

Load next parameter byte.

6452

BIT 0,(HL) CB 46

Test bit 0 of drive flags.

6454

RET Z C8

If Z FLAG (bit clear), RETURN.

6455

OR (HL) B6

OR parameter with drive flags.

6456

LD (HL),A 77

Store updated flags.

6457

RET C9

RETURN to caller.

Handle end-of-text (03H) - generate drive spec from drive count.

6458

CP 03H FE 03

Compare with 03H (ETX - end of text).

645A

JR NZ,643AH 20 DE

If NZ FLAG (not ETX), JUMP back to 643AH continue scan.

645C

LD A,(HL) 7E

Load drive count from flags.

645D

CP 06H FE 06

Compare with 6 (max drives).

645F

JR C,6474H 38 13

If C FLAG (less than 6), JUMP to 6474H check ILF/XLF.

6461

LD A,(BC) 0A

Load parameter byte.

6462

OR A B7

Test if zero.

6463

INC BC 03

Advance parameter pointer.

6464

JR NZ,6468H 20 02

If NZ FLAG (non-zero), JUMP to 6468H.

6466

SET 0,(HL) CB C6

Set bit 0 of drive flags (single drive mode).

6468

ADD 30H C6 30

Add 30H ('0') to convert to ASCII digit.

646A

LD (DE),A 12

Store ASCII drive number in command buffer.

646B

DEC DE 1B

Move back in buffer.

646C

EX DE,HL EB

HL = buffer pointer.

646D

LD (HL),3AH 36 3A

Store ':' (colon) before drive number.

646F

INC HL 23

Advance pointer.

6470

INC HL 23

Advance pointer (past drive digit).

6471

LD (HL),03H 36 03

Store 03H (ETX) to terminate.

6473

RET C9

RETURN to caller.

Check if ILF/XLF options allow filespec parsing.

6474

BIT 0,A CB 47

Test bit 0 of drive count.

6476

JR NZ,6482H 20 0A

If NZ FLAG (odd), JUMP to 6482H error.

6478

LD A,(5997H) 3A 97 59

Load option flags from 5997H.

647B

AND C0H E6 C0

Mask bits 6-7 (ILF/XLF flags).

647D

LD H,B 60

Copy BC to HL.

647E

LD L,C 69

HL = BC (parameter pointer).

647F

JP Z,5538H CA 38 55

If Z FLAG (no ILF/XLF), JUMP to 5538H setup drive.

6482

JP 5200H C3 00 52

JUMP to 5200H error handler (bad parameter).

64A3H - Override Parameter Table (DATA)

Table of parameter override addresses used during COPY/FORMAT operations. Each entry is 3 bytes: count + address. Referenced by 63DDH during parameter override processing.

64A3

DEFB 04H 04

Count: 4 entries for first override.

64A4

DEFW 59BAH BA 59

Address: 59BAH (source parameter area).

64A6

DEFB 00H 00

Terminator/padding.

64A7

DEFW 59C8H C8 59

Address: 59C8H (destination parameter area).

64A9

DEFB 00H 00

Terminator/padding.

64AA

DEFW 59CDH CD 59

Address: 59CDH (track count storage).

64AC

DEFW 59CEH CE 59

Address: 59CEH (sector count storage).

64AE

DEFB 00H 00

End of table marker.

64B0H - Clear System Buffer

Clears 256 bytes of the system buffer at 4200H by writing the value in A. Uses DJNZ loop with B=0 (256 iterations).

64B0

LD HL,4200H 21 00 42

Load HL with 4200H (system buffer).

64B3

LD B,00H 06 00

Load B with 0 (256 iterations via wraparound).

64B5

LD (HL),A 77

Store A at buffer location.

64B6

INC HL 23

Advance buffer pointer.

64B7

DJNZ 64B5H 10 FC

Decrement B, JUMP to 64B5H if not zero.

64B9

RET C9

RETURN to caller.

64BAH - Boot Sector Loader Entry

This is the bootstrap loader code that gets written to the boot sector during FORMAT. It loads the system from disk into memory. The code runs at low memory addresses after being loaded by the ROM bootstrap. Contains FDC (Floppy Disk Controller) programming sequences.

64BA

DEFB 00H 00

NOP placeholder (adjusted during FORMAT).

64BB

CP 11H FE 11

Compare A with 11H (check for Model I/III).

64BD

DI F3

Disable interrupts during disk I/O.

64BE

LD HL,37ECH 21 EC 37

Load HL with 37ECH (FDC command register).

64C1

LD (HL),FEH 36 FE

Write FEH to FDC (drive select).

WD 1771 FDC Command Code: FEH (11111110)
Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0	Function/Parameters
1	1	1	1	0	1	0	0	Command=Write Track (Format) Bit 7-4: Write Command (1111) Bit 3-0: Specific Code (0100) On its own, this would be an invalid command to send to the stock FDC. HOWEVER, as Blair Robbins has pointed out, this is a perfectly valid command to a Percom Doubler, and it sets the doubler to use the 1771 single density chip instead of the 1791 double density chip.

64C3

LD (HL),D0H 36 D0

Write D0H to FDC (force interrupt/reset).

WD 1771 FDC Command Code: D0H (11010000)
Bit 7	Bit 6	Bit 5	Bit 4	I3	I2	I1	I0	Function/Parameters
1	1	0	1	0	0	0	0	Command=Force Interrupt Bit 7-4: Command Code (1101) I3: 1=Interrupt Immediately I2: 1=Interrupt on the next Index Pulse I1: 1=Interrupt the next time Ready goes to Not Ready I0: 1=Interrupt the next time Not Ready goes to Ready

64C5

INC HL 23

Advance to next FDC register which is the FDC Track Register.

64C6

LD (HL),00H 36 00

Write 00H (track 0).

64C8

INC HL 23

Advance to the next FDC register which is the FDC sector register.

64C9

LD (HL),80H 36 80

Write 80H (sector/data mark).

64CB

LD DE,0005H 11 05 00

Load DE with 5 (sector count).

64CE

EXX D9

Switch to alternate registers.

64CF

LD SP,41E0H 31 E0 41

Set stack to 41E0H (safe area during load).

64D2

LD HL,51FFH 21 FF 51

Load HL with 51FFH (load address - 1).

64D5

CALL 4252H CD 52 42

CALL 4252H (ROM: read byte from FDC).

64D8

CP 20H FE 20

Compare with 20H (space - end marker?).

64DA

LD B,A 47

Save byte in B.

64DB

JR NC,6506H 30 29

If NC FLAG (>= 20H), JUMP to 6506H error.

64DD

LD D,A 57

D = block type/count.

64DE

CALL 4252H CD 52 42

CALL 4252H read next byte (count low).

64E1

LD C,A 4F

C = count low byte.

64E2

CALL 4252H CD 52 42

CALL 4252H read next byte (address low).

64E5

LD E,A 5F

E = address low byte.

64E6

DJNZ 64FAH 10 12

Decrement B, if not zero JUMP to 64FAH.

64E8

CALL 4252H CD 52 42

CALL 4252H read address high byte.

64EB

LD D,A 57

D = address high byte.

64EC

DEC C 0D

Decrement count.

64ED

DEC C 0D

Decrement count again.

64EE

INC L 2C

Increment L (source pointer low).

64EF

CALL Z,4255H CC 55 42

If Z FLAG (L wrapped), CALL 4255H handle page cross.

64F2

LD A,(HL) 7E

Load byte from source buffer.

64F3

LD (DE),A 12

Store to destination address.

64F4

INC DE 13

Advance destination pointer.

64F5

DEC C 0D

Decrement byte count.

64F6

JR NZ,64EEH 20 F6

If NZ FLAG (more bytes), JUMP to 64EEH.

64F8

JR 64D5H 18 DB

JUMP to 64D5H for next block.

64FA

DJNZ 64F5H 10 F9

Decrement B, if not zero JUMP to 64F5H.

64FC

CALL 4252H CD 52 42

CALL 4252H read next header byte.

64FF

LD D,A 57

D = header byte.

6500

LD A,(DE) 1A

Load byte at address in DE.

6501

CP A5H FE A5

Compare with A5H (signature byte).

6503

INC DE 13

Advance pointer.

6504

PUSH DE D5

Push entry address.

6505

RET Z C8

If Z FLAG (signature matched), RETURN to system entry.

6506

LD HL,42E5H 21 E5 42

Load HL with 42E5H (error message address).

6509

JP 42C3H C3 C3 42

JUMP to 42C3H (ROM: display error and halt).

650CH - FDC Sector Read Subroutine (Boot Loader Helper)

This subroutine is called during the boot process to read sectors from the floppy disk. It handles buffer pointer management and interfaces with the WD1771 FDC (Floppy Disk Controller). The addresses 37E1H, 37ECH, 37EEH, and 37EFH are the FDC hardware registers. This code runs from the boot sector after being loaded into memory.

650C

INC L 2C

Increment the low byte of HL (buffer pointer). This advances through the sector buffer one byte at a time.

650D

LD A,(HL) 7E

Load the byte at the current buffer position into Register A.

650E

RET NZ C0

If the byte is non-zero (NZ FLAG set), RETURN to caller with the byte in A. A zero byte indicates end-of-buffer or special marker.

650F

EXX D9

Switch to alternate register set (BC', DE', HL'). The primary registers are preserved while the FDC operation proceeds.

6510

LD B,0AH 06 0A

Load B with 10 (0AH). This is the retry counter for FDC read operations.

[RETRY LOOP START] - The following code attempts to read a sector from the FDC, retrying up to 10 times on failure.

6512

LD HL,37E1H 21 E1 37

Load HL with 37E1H (FDC Drive Select Latch). This register controls which drive is selected and motor status.

6515

LD (HL),01H 36 01

Write 01H to the drive select latch, selecting Drive 0 with motor on.

6517

PUSH DE D5

Save DE (contains sector address) to the stack.

6518

PUSH BC C5

Save BC (B = retry counter) to the stack.

6519

LD A,E 7B

Load A with E (sector number component).

651A

SUB 00H D6 00

Subtract 00H from A. This is a self-modifying code target - the operand at 651BH is patched at runtime to hold the sectors-per-track value for sector number calculation.

651C

JR C,6521H 38 03

If Carry FLAG set (sector number < sectors-per-track), JUMP to 6521H to continue without adjustment.

651E

LD E,A 5F

Store adjusted sector number back into E.

651F

LD (HL),09H 36 09

Write 09H to drive select (37E1H), selecting Drive 0 with side 1 (for double-sided disks).

6521

LD HL,37ECH 21 EC 37

Load HL with 37ECH (FDC Command/Status Register).

6524

CALL 42CEH CD CE 42

CALL 42CEH - ROM routine to wait for FDC ready and handle timing.

6527

LD (37EEH),DE ED 53 EE 37

Write DE to 37EEH (FDC Sector Register). D = track number, E = sector number.

652B

LD (HL),1BH 36 1B

Write 1BH to FDC Command Register - this is a SEEK command with verify.

WD 1771 FDC Command Code: 1BH (00011011)								Function Description
Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0		Summary of Bits
0	0	0	1	1	0	1	1		Command=Seek Bit 7-4: Command Code (0001) h=1: Enable Head Load/Settle delay V=0: No verification r1,r0=11: Stepping Motor Rate = 15ms

652D

CALL 42CEH CD CE 42

CALL 42CEH - Wait for SEEK command to complete.

6530

LD (HL),88H 36 88

Write 88H to FDC Command Register - READ SECTOR command.

WD 1771 FDC Command Code: 88H (10001000)								Function Description
Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0		Summary of Bits
1	0	0	0	1	0	0	0		Command=Read Sector Bit 7-5: Read Command (100) m=0: Single Record b=1: IBM format E=0: Assume Head Already Engaged, no Delay Remainder: Unused (00)

6532

LD DE,37EFH 11 EF 37

Load DE with 37EFH (FDC Data Register address).

6535

LD BC,5100H 01 00 51

Load BC with 5100H. B = 51H (81 decimal) is the buffer page high byte, C = 00H is the buffer offset. This sets up the destination for sector data.

6538

CALL 42D7H CD D7 42

CALL 42D7H - ROM routine to wait for FDC DRQ (Data Request) signal.

653B

LD A,(HL) 7E

Load A with FDC Status Register value (HL still points to 37ECH).

7	6	5	4	3	2	1	0
Not Ready	Protected	Head Loaded	Seek Error	CRC Error	Track 00	Index	Busy

653C

AND 83H E6 83

Mask with 83H to isolate BUSY (bit 0), DRQ (bit 1), and NOT READY (bit 7) status bits.

653E

JP PO,4281H E2 81 42

If Parity Odd (odd number of bits set in result), JUMP to 4281H - ROM error handler. This detects abnormal FDC states.

[DATA TRANSFER LOOP] - Read bytes from FDC data register as they become available.

6541

LD A,(DE) 1A

Load A with byte from FDC Data Register (37EFH).

6542

LD (BC),A 02

Store the byte to the sector buffer at address in BC.

6543

INC BC 03

Increment buffer pointer BC.

6544

BIT 1,(HL) CB 4E

Test bit 1 of FDC Status (DRQ - Data Request). If set, more data is available.

6546

JP NZ,4287H C2 87 42

If NZ FLAG (DRQ active), JUMP to 4287H - ROM routine to handle rapid data transfer.

6549

BIT 1,(HL) CB 4E

Test DRQ bit again (timing window check).

654B

JP NZ,4287H C2 87 42

If NZ FLAG (DRQ still active), JUMP to 4287H.

654E

BIT 1,(HL) CB 4E

Test DRQ bit a third time.

6550

JR NZ,6541H 20 EF

If NZ FLAG (DRQ active), JUMP back to 6541H to read next byte.

6552

BIT 0,(HL) CB 46

Test bit 0 of FDC Status (BUSY). If clear, operation is complete.

6554

JR Z,655EH 28 08

If Z FLAG (not busy), JUMP to 655EH to complete the read.

6556

BIT 1,(HL) CB 4E

Test DRQ bit again while still busy.

6558

JR NZ,6541H 20 E7

If NZ FLAG (DRQ active), JUMP to 6541H to read byte.

655A

BIT 7,(HL) CB 7E

Test bit 7 of FDC Status (NOT READY). If set, drive is not ready.

655C

JR Z,6544H 28 E6

If Z FLAG (drive is ready), JUMP back to 6544H to continue polling.

[READ COMPLETE] - Sector read finished. Check for errors and update pointers.

655E

LD A,(HL) 7E

Load A with final FDC Status value.

655F

LD (HL),D0H 36 D0

Write D0H to FDC Command Register - FORCE INTERRUPT to terminate any pending operation.

WD 1771 FDC Command Code: D0H (11010000)								Function Description
Bit 7	Bit 6	Bit 5	Bit 4	I3	I2	I1	I0		Summary of Bits
1	1	0	1	0	0	0	0		Command=Force Interrupt Bit 7-4: Command Code (1101) I3=0: No immediate interrupt I2=0: No interrupt on Index Pulse I1=0: No interrupt on Ready change I0=0: No interrupt on Not Ready change

6561

POP BC C1

Restore BC (B = retry counter) from stack.

6562

POP DE D1

Restore DE (sector address) from stack.

6563

AND FCH E6 FC

Mask status with FCH to isolate error bits (CRC error, seek error, lost data, etc.). Bits 0-1 (BUSY, DRQ) are cleared.

6565

JR NZ,6573H 20 0C

If NZ FLAG (error occurred), JUMP to 6573H for error recovery/retry.

6567

INC E 1C

Increment sector number in E for next sector.

6568

LD A,E 7B

Load A with new sector number.

6569

SUB 00H D6 00

Subtract sectors-per-track value. Self-modifying code target at 656AH - operand is patched at runtime.

656B

JR NZ,6570H 20 03

If NZ FLAG (not at track boundary), JUMP to 6570H to continue.

656D

INC D 14

Increment track number in D (crossed to next track).

656E

LD E,00H 1E 00

Reset sector number to 0 for new track. Self-modifying code target at 656FH - may be patched to 01H for 1-based sector numbering.

6570

EXX D9

Switch back to primary register set.

6571

LD A,(HL) 7E

Load next byte from sector buffer (HL was preserved in primary set).

6572

RET C9

RETURN to caller with data byte in A.

6573H - FDC Error Recovery and Retry

This section handles FDC read errors. It sends a RESTORE command to recalibrate the head to track 0, then retries the operation. If all retries fail, it enters a fatal error display loop.

6573

CALL 42D7H CD D7 42

CALL 42D7H - ROM routine to wait for FDC ready.

6576

LD (HL),0BH 36 0B

Write 0BH to FDC Command Register - RESTORE command to seek to track 0.

WD 1771 FDC Command Code: 0BH (00001011)								Function Description
Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0		Summary of Bits
0	0	0	0	1	0	1	1		Command=Restore Bit 7-4: Command Code (0000) h=1: Enable Head Load/Settle delay V=0: No verification of Track 0 ID r1,r0=11: Stepping Motor Rate = 15ms

6578

DJNZ 6512H 10 98

Decrement B (retry counter). If NZ FLAG (retries remaining), JUMP to 6512H to retry the read.

[FATAL ERROR] - All retries exhausted. Display error message and halt.

657A

LD HL,42DDH 21 DD 42

Load HL with 42DDH - pointer to video display routine or error message table in ROM.

657D

LD A,(HL) 7E

[DISPLAY LOOP] Load character from message.

657E

CP 03H FE 03

Compare with 03H (ETX - End of Text marker).

6580

JR Z,657DH 28 FB

If Z FLAG (end of message), JUMP to 657DH - infinite loop (halt with message displayed).

6582

INC HL 23

Advance to next character in message.

6583

CALL 0033H CD 33 00

CALL 0033H - ROM routine to display character in A on screen.

6586

JR 657DH 18 F5

JUMP to 657DH to continue displaying message.

6588H - Wait for FDC Not Busy

This short subroutine waits for the FDC to finish any pending operation by polling the BUSY bit (bit 0) of the status register.

6588

CALL 42D7H CD D7 42

CALL 42D7H - ROM routine for FDC timing/wait.

658B

BIT 0,(HL) CB 46

[BUSY WAIT LOOP] Test bit 0 of FDC Status Register (BUSY flag).

658D

JR NZ,658BH 20 FC

If NZ FLAG (still busy), JUMP to 658BH to keep waiting.

658F

LD A,(HL) 7E

Load A with final FDC Status value.

6590

RET C9

RETURN to caller with status in A.

6591H - Short Delay Loop

A simple timing delay loop that counts down from 6 to 0. Used to provide brief delays for FDC timing requirements.

6591

LD A,06H 3E 06

Load A with 6 as the delay counter.

6593

DEC A 3D

[DELAY LOOP] Decrement the counter.

6594

JR NZ,6593H 20 FD

If NZ FLAG (counter not zero), JUMP to 6593H to continue delay.

6596

RET C9

RETURN to caller.

6597H - Boot Error Message Strings

This section contains the error message strings displayed during boot failures. The strings are prefixed with cursor positioning codes (1CH = cursor home, 1FH = cursor down) and terminated with 03H (ETX - End of Text).

6597

DEFB 1CH 1C

Cursor control: HOME (move cursor to top-left).

6598

DEFB 1FH 1F

Cursor control: CURSOR DOWN.

6599

DEFB 'E' 45

ASCII character E.

659A

DEFB 'R' 52

ASCII character R.

659B

DEFB 'R' 52

ASCII character R.

659C

DEFB 'O' 4F

ASCII character O.

659D

DEFB 'R' 52

ASCII character R.

659E

DEFB 03H 03

ETX (End of Text) - string terminator. Complete string: "ERROR"

659F

DEFB 1CH 1C

Cursor control: HOME.

65A0

DEFB 1FH 1F

Cursor control: CURSOR DOWN.

65A1

DEFB 'N' 4E

ASCII character N.

65A2

DEFB 'O' 4F

ASCII character O.

65A3

DEFB ' ' 20

ASCII character SPACE.

65A4

DEFB 'S' 53

ASCII character S.

65A5

DEFB 'Y' 59

ASCII character Y.

65A6

DEFB 'S' 53

ASCII character S.

65A7

DEFB 03H 03

ETX (End of Text) - string terminator. Complete string: "NO SYS"

65B0H - Boot Sector FCB Template: BOOT/SYS

This is an FCB (File Control Block) template for the BOOT/SYS file. During FORMAT, this data is copied and modified to create the directory entry for the boot system file. The FCB structure follows the standard NEWDOS/80 directory entry format.

65B0

DEFB 00H 00

FCB attribute/status byte (00H = normal file).

65B1

DEFB 00H 00

Reserved byte.

65B2

DEFB 00H 00

Reserved byte.

65B3

DEFB 00H 00

Reserved byte.

65B4

DEFB 00H 00

Reserved byte.

65B5

DEFB 00H 00

Reserved byte.

65B6

DEFB 00H 00

Reserved byte.

65B7

DEFB 00H 00

Sectors per track - patched at runtime based on disk format.

65B8

DEFB 00H 00

Disk density flag - patched at runtime.

65B9

DEFB 00H 00

Disk configuration byte - patched at runtime.

65BA

DEFB 5EH 5E

GAT (Granule Allocation Table) pointer or file attribute.

65BB

DEFB 00H 00

Reserved byte.

65BC

DEFB 00H 00

Reserved byte.

65BD

DEFB 00H 00

Reserved byte.

65BE

DEFB 00H 00

Reserved byte.

65BF

DEFB 'B' 42

Filename character 1: B

65C0

DEFB 'O' 4F

Filename character 2: O

65C1

DEFB 'O' 4F

Filename character 3: O

65C2

DEFB 'T' 54

Filename character 4: T

65C3

DEFB ' ' 20

Filename character 5: SPACE

65C4

DEFB ' ' 20

Filename character 6: SPACE

65C5

DEFB ' ' 20

Filename character 7: SPACE

65C6

DEFB ' ' 20

Filename character 8: SPACE

65C7

DEFB 'S' 53

Extension character 1: S

65C8

DEFB 'Y' 59

Extension character 2: Y

65C9

DEFB 'S' 53

Extension character 3: S. Complete filename: BOOT /SYS

65CA

DEFB 60H 60

File attributes byte (60H = system file, invisible).

65CB

DEFB 7FH 7F

EOF offset within last sector.

65CC

DEFB 1FH 1F

Logical record length or flag byte.

65CD

DEFB B2H B2

Extent/allocation information.

65CE

DEFB 05H 05

Extent/allocation information.

65CF

DEFB 00H 00

Reserved byte.

65D0H - Boot Sector Padding

Padding bytes and filler data in the boot sector template area.

65D0

DEFB 00H 00

Padding byte.

65D1

DEFB 00H 00

Padding byte.

65D2

DEFB FFH FF

Filler byte (FFH).

65D3

DEFB FFH FF

Filler byte (FFH).

65D4

DEFB FFH FF

Filler byte (FFH).

65D5

DEFB FFH FF

Filler byte (FFH).

65D6

DEFB FFH FF

Filler byte (FFH).

65D7

DEFB FFH FF

Filler byte (FFH).

65D8

DEFB FFH FF

Filler byte (FFH).

65D9

DEFB FFH FF

Filler byte (FFH).

65DAH - Boot Sector FCB Template: DIR/SYS

FCB template for the DIR/SYS system file (directory handler). This is written to the disk directory during FORMAT.

65DA

DEFB 5DH 5D

GAT pointer or attribute byte.

65DB

DEFB 00H 00

Reserved byte.

65DC

DEFB 00H 00

Reserved byte.

65DD

DEFB 00H 00

Reserved byte.

65DE

DEFB 00H 00

Reserved byte.

65DF

DEFB 'D' 44

Filename character 1: D

65E0

DEFB 'I' 49

Filename character 2: I

65E1

DEFB 'R' 52

Filename character 3: R

65E2

DEFB ' ' 20

Filename character 4: SPACE

65E3

DEFB ' ' 20

Filename character 5: SPACE

65E4

DEFB ' ' 20

Filename character 6: SPACE

65E5

DEFB ' ' 20

Filename character 7: SPACE

65E6

DEFB ' ' 20

Filename character 8: SPACE

65E7

DEFB 'S' 53

Extension character 1: S

65E8

DEFB 'Y' 59

Extension character 2: Y

65E9

DEFB 'S' 53

Extension character 3: S. Complete filename: DIR /SYS

65EA

DEFB A7H A7

File attributes byte (A7H = system file with special flags).

65EB

DEFB 1DH 1D

EOF offset or record length.

65EC

DEFB F9H F9

Extent/allocation information.

65ED

DEFB E5H E5

Extent/allocation information.

65EE

DEFB 0AH 0A

Sectors count - patched at runtime based on disk format.

65EF

DEFB 00H 00

Reserved byte.

65F0H - Boot Sector Configuration Data

Configuration data for the boot sector, including track/sector information that gets patched during FORMAT based on the target disk format.

65F0

DEFW FF01H 01 FF

Track/sector configuration word - patched at runtime. Low byte = first sector, high byte = last track.

65F2

DEFB FFH FF

Filler byte (FFH).

65F3

DEFB FFH FF

Filler byte (FFH).

65F4

DEFB FFH FF

Filler byte (FFH).

65F5

DEFB FFH FF

Filler byte (FFH).

65F6

DEFB FFH FF

Filler byte (FFH).

65F7

DEFB FFH FF

Filler byte (FFH).

65F8

DEFB FFH FF

Filler byte (FFH).

65F9

DEFB FFH FF

Filler byte (FFH). End of boot sector template area.

65FAH - COPY Command: File Copy Handler

This is the entry point for the COPY command's file copy operation. It handles the TO parameter parsing and sets up flags for the copy operation.

65FA

CALL 6392H CD 92 63

CALL 6392H - Parse destination filespec (TO parameter).

65FD

JP NC,5218H D2 18 52

If NC FLAG (parse error), JUMP to 5218H - error handler.

6600

CALL 63A0H CD A0 63

CALL 63A0H - Validate filespec and set up FCB.

6603

PUSH HL E5

Save HL (command line pointer) to stack.

6604

LD HL,5997H 21 97 59

Load HL with 5997H - address of COPY command flags.

6607

SET 2,(HL) CB D6

Set bit 2 of flags - indicates destination filespec is valid.

6609

POP HL E1

Restore HL (command line pointer) from stack.

660A

CALL 6EB5H CD B5 6E

CALL 6EB5H - Skip whitespace and check for more parameters.

660D

CALL C,4F95H DC 95 4F

If Carry FLAG set (more parameters), CALL 4F95H - parse additional options.

6610

CALL 6FB8H CD B8 6F

CALL 6FB8H - Validate source/destination drive compatibility.

6613

CALL 6EB5H CD B5 6E

CALL 6EB5H - Check for additional parameters.

6616

JR NC,661FH 30 07

If NC FLAG (no more parameters), JUMP to 661FH.

6618

CALL 5025H CD 25 50

CALL 5025H - Parse numeric parameter (file count or size).

661B

LD (5981H),DE ED 53 81 59

Store parsed value to 5981H (copy parameter storage).

661F

LD B,40H 06 40

Load B with 40H (64 decimal) - option flags mask.

6621

CALL 4EA7H CD A7 4E

CALL 4EA7H - Process COPY command options and validate.

6624

LD HL,5994H 21 94 59

Load HL with 5994H - address of operation status flags.

6627

LD A,(HL) 7E

Load A with current status flags.

6628

AND F9H E6 F9

Mask with F9H to test specific flag bits.

662A

JR NZ,6630H 20 04

If NZ FLAG (flags set), JUMP to 6630H to continue.

662C

LD A,(HL) 7E

Load A with status flags again.

662D

OR 80H F6 80

Set bit 7 (default option flag).

662F

LD (HL),A 77

Store updated flags.

6630

CALL 63B3H CD B3 63

CALL 63B3H - Initialize file operation structures.

6633

LD HL,6DF3H 21 F3 6D

Load HL with 6DF3H - address of "Copying" message string.

6636

CALL 4467H (SYS0) - Display message string.

6639

CALL 6710H CD 10 67

CALL 6710H - Calculate and display disk space requirements.

663C

CALL 4DF3H CD F3 4D

CALL 4DF3H - Read PDRIVE table from disk.

663F

LD HL,552DH 21 2D 55

Load HL with 552DH - return address for copy completion.

6642

PUSH HL E5

Push return address to stack (will return here after copy).

6643H - Initialize Copy Operation

This routine initializes the copy operation, checking various flags to determine the copy mode and whether disk swapping prompts are needed for single-drive copies.

6643

CALL 67C3H CD C3 67

CALL 67C3H - Set up FCB and disk parameters for copy.

6646

LD A,(5997H) 3A 97 59

Load A with COPY command flags from 5997H.

6649

BIT 3,A CB 5F

Test bit 3 - special copy mode flag.

664B

RET NZ C0

If NZ FLAG (special mode active), RETURN - copy already set up.

664C

LD A,(5996H) 3A 96 59

Load A with additional flags from 5996H.

664F

BIT 7,A CB 7F

Test bit 7 - verify mode flag.

6651

RET NZ C0

If NZ FLAG (verify mode), RETURN.

6652

LD DE,0000H 11 00 00

Load DE with 0 - clear counter/parameter.

6655

CALL 5784H CD 84 57

CALL 5784H - Initialize disk I/O parameters.

6658

LD A,(5994H) 3A 94 59

Load A with operation status from 5994H.

665B

BIT 1,A CB 4F

Test bit 1 - multi-file copy flag.

665D

RET NZ C0

If NZ FLAG (multi-file mode), RETURN.

665E

LD HL,6DDAH 21 DA 6D

Load HL with 6DDAH - address of prompt message.

6661

CALL 4467H (SYS0) - Display prompt message.

6664

CALL 67AAH CD AA 67

CALL 67AAH - Get user response or wait for keypress.

6667

LD DE,6EB5H 11 B5 6E

Load DE with 6EB5H - default value or parameter address.

666A

LD BC,0002H 01 02 00

Load BC with 2 - parameter count or size.

666D

CALL Z,67B4H CC B4 67

If Z FLAG (default response), CALL 67B4H to use defaults.

6670

If NZ FLAG (error or cancel), JUMP to 521AH error handler.

6673

LD A,FFH 3E FF

Load A with FFH - all bits set (full track/all sectors flag).

6675

CALL 64B0H CD B0 64

CALL 64B0H - Set up disk track parameters.

6678

LD DE,(59D1H) ED 5B D1 59

Load DE with value from 59D1H - disk geometry parameter.

667C

LD HL,4200H 21 00 42

Load HL with 4200H - sector buffer address.

667F

LD (5B1AH),HL 22 1A 5B

Store buffer address to 5B1AH (FCB buffer pointer).

6682

LD C,L 4D

Load C with L (00H - buffer low byte).

6683

PUSH HL E5

Save buffer address to stack.

6684

CALL 5762H CD 62 57

CALL 5762H - Read sector into buffer.

6687

POP HL E1

Restore buffer address from stack.

6688

SET 0,(HL) CB C6

Set bit 0 of first byte in buffer (directory entry flag).

668A

LD A,(59CDH) 3A CD 59

Load A with value from 59CDH - sectors per track.

668D

LD (59C5H),A 32 C5 59

Store to 59C5H - working sectors per track.

6690

LD HL,(4399H) 2A 99 43

Load HL with pointer from 4399H (system area pointer).

6693

LD (HL),A 77

Store sectors per track to system area.

6694

LD B,00H 06 00

Load B with 0 - initialize counter.

6696

LD E,A 5F

Load E with sectors per track.

6697

LD A,(59CEH) 3A CE 59

Load A with value from 59CEH - total tracks.

669A

LD C,A 4F

Load C with total tracks.

669B

PUSH DE D5

Save DE (sectors per track) to stack.

669C

LD HL,4200H 21 00 42

Load HL with 4200H - sector buffer address.

669F

CALL 621CH CD 1C 62

CALL 621CH - Calculate disk capacity or allocation.

66A2

LD HL,597EH 21 7E 59

Load HL with 597EH - source data area.

66A5

LD DE,42CBH 11 CB 42

Load DE with 42CBH - destination in sector buffer.

66A8

LD BC,0016H 01 16 00

Load BC with 22 (16H) - bytes to copy.

66AB

LDIR ED B0

Block copy 22 bytes from (HL) to (DE).

66AD

POP HL E1

Restore HL (was DE - sectors per track).

66AE

LD A,(59CAH) 3A CA 59

Load A with value from 59CAH - granule size.

66B1

LD H,A 67

Load H with granule size.

66B2

RLCA 07

Rotate left (multiply by 2).

66B3

RLCA 07

Rotate left again (multiply by 4).

66B4

ADD A,H 84

Add original value (A = granule_size * 5).

66B5

CALL 4C92H (SYS0) - Multiply or calculate offset.

66B8

LD (5B21H),HL 22 21 5B

Store result to 5B21H - allocation table pointer.

66BB

LD C,00H 0E 00

Load C with 0 - initialize sector counter.

66BD

JR 66FBH 18 3C

JUMP to 66FBH to begin sector write loop.

66BFH - Write System Sectors Loop

This loop writes the system sectors to the disk during FORMAT. It writes the boot sector, directory, and system file entries. The loop processes sectors 0-9 (10 sectors total).

66BF

PUSH BC C5

[SECTOR WRITE LOOP] Save BC (C = sector counter) to stack.

66C0

XOR A AF

Clear A (set to 0).

66C1

CALL 64B0H CD B0 64

CALL 64B0H - Set track 0 for boot sector writes.

66C4

LD A,C 79

Load A with current sector number from C.

66C5

DEC A 3D

Decrement A (check if sector 1).

66C6

JR NZ,66E6H 20 1E

If NZ FLAG (not sector 1), JUMP to 66E6H to check other sectors.

Sector 1 processing - set up GAT (Granule Allocation Table) header.

66C8

LD HL,4200H 21 00 42

Load HL with 4200H - sector buffer address.

66CB

LD (HL),A2H 36 A2

Write A2H to buffer - GAT signature byte 1.

66CD

INC HL 23

Advance buffer pointer.

66CE

LD (HL),C4H 36 C4

Write C4H to buffer - GAT signature byte 2. Together A2C4H identifies a valid GAT sector.

66D0

LD A,(59CEH) 3A CE 59

Load A with total tracks from 59CEH.

66D3

SUB 02H D6 02

Subtract 2 (reserved tracks for system).

66D5

LD C,A 4F

Save result in C (usable tracks).

66D6

RLCA 07

Rotate left (multiply by 2).

66D7

RLCA 07

Rotate left again (multiply by 4).

66D8

ADD A,C 81

Add original (A = usable_tracks * 5).

66D9

LD (421FH),A 32 1F 42

Store calculated value to 421FH (GAT size in buffer).

66DC

ADD 0AH C6 0A

Add 10 to get offset for directory entry.

66DE

LD (65EEH),A 32 EE 65

Patch the DIR/SYS FCB template at 65EEH with sector count.

66E1

LD (670CH),A 32 0C 67

Store value at 670CH for later reference.

66E4

JR 66FAH 18 14

JUMP to 66FAH to write this sector.

Check for directory sectors (sectors 2-3) to copy FCB templates.

66E6

LD HL,65BAH 21 BA 65

Load HL with 65BAH - BOOT/SYS FCB template address.

66E9

CP 02H FE 02

Compare A with 2 (sector 2 = first directory sector).

66EB

JR C,66F2H 38 05

If Carry FLAG (sector < 2), JUMP to 66F2H to copy FCB.

66ED

JR NZ,66FAH 20 0B

If NZ FLAG (sector > 2), JUMP to 66FAH (skip FCB copy).

66EF

LD HL,65DAH 21 DA 65

Load HL with 65DAH - DIR/SYS FCB template address (for sector 2).

66F2

LD DE,4200H 11 00 42

Load DE with 4200H - sector buffer destination.

66F5

LD BC,0020H 01 20 00

Load BC with 32 (20H) - FCB entry size.

66F8

LDIR ED B0

Block copy 32 bytes of FCB template to buffer.

66FA

POP BC C1

Restore BC (sector counter) from stack.

66FB

SET 0,(IX+00H) DD CB 00 C6

Set bit 0 of (IX+00H) - mark sector as modified/needs write.

66FF

CALL 57D4H CD D4 57

CALL 57D4H - Write sector to disk.

6702

RES 0,(IX+00H) DD CB 00 86

Clear bit 0 of (IX+00H) - mark sector write complete.

6706

If NZ FLAG (write error), JUMP to 521AH error handler.

6709

INC C 0C

Increment sector counter.

670A

LD A,C 79

Load A with current sector count.

670B

CP 0AH FE 0A

Compare with 10 (0AH) - total system sectors. Self-modifying code target at 670CH - may be patched.

670D

JR C,66BFH 38 B0

If Carry FLAG (more sectors to write), JUMP to 66BFH.

670F

RET C9

RETURN - all system sectors written.

6710H - Calculate Disk Space Requirements

This routine calculates and displays the disk space requirements for a copy or format operation. It reads disk parameters and calculates free space, sectors needed, etc.

6710

LD HL,59C5H 21 C5 59

Load HL with 59C5H - disk parameter block address.

6713

PUSH IX DD E5

Save IX to stack.

6715

PUSH HL E5

Push HL to stack.

6716

POP IX DD E1

Pop into IX (IX now points to disk parameter block at 59C5H).

6718

LD A,(IX+04H) DD 7E 04

Load A with (IX+04H) = byte at 59C9H (sectors per granule).

671B

LD L,(IX+03H) DD 6E 03

Load L with (IX+03H) = byte at 59C8H (granules per track).

671E

CALL 4C92H (SYS0) - Multiply A * L, result in HL.

6721

LD (IX+0AH),L DD 75 0A

Store L to (IX+0AH) = 59CFH.

6724

LD (IX+0BH),H DD 74 0B

Store H to (IX+0BH) = 59D0H.

6727

CALL 5CF2H CD F2 5C

CALL 5CF2H - Additional disk space calculation.

672A

LD (IX+0CH),L DD 75 0C

Store L to (IX+0CH) = 59D1H.

672D

LD (IX+0DH),H DD 74 0D

Store H to (IX+0DH) = 59D2H.

6730

LD A,(IX+05H) DD 7E 05

Load A with (IX+05H) = byte at 59CAH (granule size).

6733

CALL 4CB4H (SYS0) - Divide or calculate ratio.

6736

OR A B7

Test A for zero.

6737

JR Z,673AH 28 01

If Z FLAG (A = 0), JUMP to 673AH.

6739

INC HL 23

Increment HL (round up).

673A

LD A,H 7C

Load A with high byte of result.

673B

OR A B7

Test if H is non-zero.

673C

JR NZ,6747H 20 09

If NZ FLAG (overflow - too many granules), JUMP to 6747H error.

673E

LD A,L 7D

Load A with low byte of granule count.

673F

CP C1H FE C1

Compare with 193 (C1H) - maximum granules per disk.

6741

LD (IX+01H),A DD 77 01

Store granule count to (IX+01H) = 59C6H.

6744

POP IX DD E1

Restore IX from stack.

6746

RET C D8

If Carry FLAG (granule count < 193), RETURN - disk is valid.

[ERROR PATH] - Disk format exceeds maximum capacity or other error.

6747

LD HL,6E57H 21 57 6E

Load HL with 6E57H - address of "Disk too large" error message.

674A

JP 5243H C3 43 52

JUMP to 5243H - display error message and abort.

674DH - Validate Disk Space for Copy

Validates that sufficient disk space exists for the copy operation.

674D

CALL 61EAH CD EA 61

CALL 61EAH - Check available disk space.

6750

RET Z C8

If Z FLAG (sufficient space), RETURN.

6751

LD A,(5994H) 3A 94 59

Load A with operation flags from 5994H.

6754

BIT 1,A CB 4F

Test bit 1 - multi-file flag.

6756

JR Z,6747H 28 EF

If Z FLAG (single file mode), JUMP to 6747H error handler.

6758

RET C9

RETURN - continue in multi-file mode (will prompt for next disk).

6759H - Patch Boot Sector Parameters

This routine patches the boot sector template with the actual disk parameters. It modifies self-modifying code targets in the boot loader to match the disk format being used.

6759

LD A,(59CBH) 3A CB 59

Load A with value from 59CBH - sectors per track configuration.

675C

LD (65B7H),A 32 B7 65

Patch 65B7H in BOOT/SYS FCB template.

675F

LD (64CAH),A 32 CA 64

Patch 64CAH in boot sector code (sector register initial value).

6762

LD A,(59CCH) 3A CC 59

Load A with value from 59CCH - disk configuration flags.

6765

LD (65B9H),A 32 B9 65

Patch 65B9H in BOOT/SYS FCB template.

6768

BIT 1,A CB 4F

Test bit 1 - double-sided disk flag.

676A

JR Z,6770H 28 04

If Z FLAG (single-sided), JUMP to 6770H.

676C

LD HL,64CDH 21 CD 64

Load HL with 64CDH - boot sector sector count location.

676F

INC (HL) 34

Increment sector count for double-sided operation.

6770

BIT 4,A CB 67

Test bit 4 - special density/format flag.

6772

JR Z,677DH 28 09

If Z FLAG (standard format), JUMP to 677DH.

6774

LD HL,64CCH 21 CC 64

Load HL with 64CCH - boot sector parameter location.

6777

INC (HL) 34

Increment parameter for special format.

6778

LD HL,656FH 21 6F 65

Load HL with 656FH - boot sector self-mod target for sector base.

677B

LD (HL),01H 36 01

Write 01H - set starting sector to 1 (instead of 0).

677D

BIT 0,A CB 47

Test bit 0 - alternate timing flag.

677F

JR Z,6786H 28 05

If Z FLAG (standard timing), JUMP to 6786H.

6781

LD HL,64C2H 21 C2 64

Load HL with 64C2H - boot sector FDC command location.

6784

SET 0,(HL) CB C6

Set bit 0 - modify FDC command timing.

6786

BIT 6,A CB 77

Test bit 6 - sectors per track modifier flag.

6788

LD A,(59C9H) 3A C9 59

Load A with value from 59C9H - sectors per granule.

678B

LD (656AH),A 32 6A 65

Patch 656AH in boot sector (self-mod target for sector count).

678E

JR Z,6791H 28 01

If Z FLAG (bit 6 clear), JUMP to 6791H.

6790

RRCA 0F

Rotate A right (divide by 2 for alternate format).

6791

LD (651BH),A 32 1B 65

Patch 651BH in boot sector (SUB instruction operand).

6794

LD A,(59CDH) 3A CD 59

Load A with value from 59CDH - first sector number.

6797

LD (64BCH),A 32 BC 64

Patch 64BCH in boot sector.

679A

LD L,A 6F

Load L with first sector number.

679B

LD A,(59CEH) 3A CE 59

Load A with value from 59CEH - total tracks.

679E

LD H,A 67

Load H with total tracks.

679F

DEC H 25

Decrement H (last track number = total - 1).

67A0

LD (65F0H),HL 22 F0 65

Store HL to 65F0H - boot sector track/sector configuration.

67A3

LD A,(59C7H) 3A C7 59

Load A with value from 59C7H - density configuration.

67A6

LD (65B8H),A 32 B8 65

Patch 65B8H in BOOT/SYS FCB template.

67A9

RET C9

RETURN - boot sector patching complete.

67AAH - Wait for User Response

Waits for user input (keypress) and sets up parameters for disk write operations.

67AA

LD BC,0000H 01 00 00

Load BC with 0 - clear counter/parameter.

67AD

CALL 67B1H CD B1 67

CALL 67B1H - set up FCB and wait.

67B0

INC BC 03

Increment BC.

67B1

LD DE,64BAH 11 BA 64

Load DE with 64BAH - boot sector template address.

67B4

LD (5B1AH),DE ED 53 1A 5B

Store DE to 5B1AH - FCB buffer pointer.

67B8

LD IX,5B17H DD 21 17 5B

Load IX with 5B17H - FCB address.

67BC

LD (5B21H),BC ED 43 21 5B

Store BC to 5B21H - allocation table pointer.

67C0

JP 57D4H C3 D4 57

JUMP to 57D4H - perform disk I/O operation.

67C3H - Copy/Format Setup Routine

This routine sets up the parameters for a COPY or FORMAT operation. It patches the boot sector, initializes the FCB, and checks various disk compatibility flags.

67C3

CALL 6759H CD 59 67

CALL 6759H - Patch boot sector parameters based on disk format.

67C6

LD IX,5B17H DD 21 17 5B

Load IX with 5B17H - FCB (File Control Block) address.

67CA

CALL 557DH CD 7D 55

CALL 557DH - Initialize FCB and open file.

67CD

LD A,(5994H) 3A 94 59

Load A with operation flags from 5994H.

67D0

LD C,A 4F

Save flags in C for later testing.

67D1

BIT 6,C CB 71

Test bit 6 - verify-only mode flag.

67D3

JP NZ,6886H C2 86 68

If NZ FLAG (verify mode), JUMP to 6886H to skip actual copy.

67D6

CALL 57C8H - Read first sector / check disk.

67D9

JR Z,67EEH 28 13

If Z FLAG (read successful), JUMP to 67EEH.

67DB

CP 05H FE 05

Compare error code with 5 (record not found).

67DD

If NZ FLAG (different error), JUMP to 521AH error handler.

67E0

BIT 7,C CB 79

Test bit 7 - format mode flag.

67E2

JP NZ,6886H C2 86 68

If NZ FLAG (format mode), JUMP to 6886H - formatting expected.

67E5

LD HL,6D94H 21 94 6D

Load HL with 6D94H - "Disk is blank" message address.

67E8

CALL 4467H (SYS0) - Display message.

67EB

JP 6880H C3 80 68

JUMP to 6880H - prompt for retry.

Disk read successful - validate disk format and copy parameters.

67EE

XOR A AF

Clear A (set to 0).

67EF

CALL 490AH CD 0A 49

CALL 490AH - Validate disk format signature.

67F2

JR Z,6806H 28 12

If Z FLAG (valid format), JUMP to 6806H.

67F4

LD L,A 6F

Save validation result in L.

67F5

LD A,C 79

Load A with flags from C.

67F6

AND 19H E6 19

Mask with 19H to test critical mode flags.

67F8

LD A,L 7D

Restore validation result to A.

67F9

If NZ FLAG (incompatible modes), JUMP to 521AH error.

67FC

LD HL,42D0H 21 D0 42

Load HL with 42D0H - disk name buffer in sector buffer.

67FF

LD B,10H 06 10

Load B with 16 (10H) - disk name length.

6801

LD (HL),3FH 36 3F

[CLEAR NAME LOOP] Write 3FH (?) to buffer - fill with wildcards.

6803

INC HL 23

Advance buffer pointer.

6804

DJNZ 6801H 10 FB

Decrement B, if NZ FLAG (more bytes), JUMP to 6801H.

6806

BIT 7,C CB 79

Test bit 7 - format mode flag.

6808

JR Z,6812H 28 08

If Z FLAG (not format mode), JUMP to 6812H.

680A

LD HL,6D82H 21 82 6D

Load HL with 6D82H - "Formatting" message address.

680D

CALL 4467H (SYS0) - Display formatting message.

6810

JR 687AH 18 68

JUMP to 687AH to begin format operation.

6812

LD A,(436CH) 3A 6C 43

Load A with system flag byte from 436CH.

6815

AND 82H E6 82

Mask with 82H to isolate specific flags.

6817

CP 80H FE 80

Compare with 80H.

6819

JR NZ,6840H 20 25

If NZ FLAG (flags don't match), JUMP to 6840H.

681B

LD A,(5996H) 3A 96 59

Load A with flags from 5996H.

681E

BIT 3,A CB 5F

Test bit 3 - date checking flag.

6820

JR Z,6840H 28 1E

If Z FLAG (no date check), JUMP to 6840H.

6822

LD A,(5995H) 3A 95 59

Load A with flags from 5995H.

6825

BIT 0,A CB 47

Test bit 0 - specific date comparison flag.

6827

JR Z,6835H 28 0C

If Z FLAG, JUMP to 6835H for date mismatch error.

6829

LD HL,(42CEH) 2A CE 42

Load HL with date value from sector buffer at 42CEH.

682C

LD DE,(597AH) ED 5B 7A 59

Load DE with expected date from 597AH.

6830

OR A B7

Clear Carry flag for comparison.

6831

SBC HL,DE ED 52

Subtract DE from HL to compare dates.

6833

JR Z,6840H 28 0B

If Z FLAG (dates match), JUMP to 6840H to continue.

[DATE MISMATCH ERROR] - Disk date doesn't match expected date.

6835

LD HL,5A44H 21 44 5A

Load HL with 5A44H - date mismatch warning message.

6838

CALL 4467H (SYS0) - Display warning message.

683B

LD A,37H 3E 37

Load A with error code 37H (date mismatch error).

683D

JUMP to 521AH - error handler.

6840H - Copy Disk Name and Date

Copies disk name and date information from the source disk to the destination parameters. Handles various copy options like preserving original dates.

6840

BIT 3,C CB 59

Test bit 3 of flags (C) - copy disk name flag.

6842

JR Z,6851H 28 0D

If Z FLAG (don't copy name), JUMP to 6851H.

6844

PUSH BC C5

Save BC to stack.

6845

LD HL,42D0H 21 D0 42

Load HL with 42D0H - disk name in sector buffer.

6848

LD DE,5983H 11 83 59

Load DE with 5983H - destination disk name buffer.

684B

LD BC,0008H 01 08 00

Load BC with 8 - disk name length.

684E

LDIR ED B0

Block copy 8 bytes of disk name.

6850

POP BC C1

Restore BC from stack.

6851

BIT 0,C CB 41

Test bit 0 of flags - copy disk date flag.

6853

JR Z,6862H 28 0D

If Z FLAG (don't copy date), JUMP to 6862H.

6855

PUSH BC C5

Save BC to stack.

6856

LD HL,42D8H 21 D8 42

Load HL with 42D8H - disk date in sector buffer.

6859

LD DE,598BH 11 8B 59

Load DE with 598BH - destination disk date buffer.

685C

LD BC,0008H 01 08 00

Load BC with 8 - date string length.

685F

LDIR ED B0

Block copy 8 bytes of disk date.

6861

POP BC C1

Restore BC from stack.

6862

BIT 4,C CB 61

Test bit 4 of flags - validate source disk flag.

6864

JR Z,6876H 28 10

If Z FLAG (no validation needed), JUMP to 6876H.

6866

LD HL,5970H 21 70 59

Load HL with 5970H - source disk validation data.

6869

CALL 624FH CD 4F 62

CALL 624FH - Validate disk against stored parameters.

686C

JR Z,6876H 28 08

If Z FLAG (validation passed), JUMP to 6876H.

686E

LD HL,5A44H 21 44 5A

Load HL with 5A44H - validation error message.

6871

CALL 692FH CD 2F 69

CALL 692FH - Display error and additional info.

6874

JR 687AH 18 04

JUMP to 687AH to prompt user.

6876

BIT 5,C CB 69

Test bit 5 of flags - prompt user flag.

6878

JR Z,6886H 28 0C

If Z FLAG (no prompt needed), JUMP to 6886H.

687A

LD HL,5A44H 21 44 5A

Load HL with 5A44H - prompt message address.

687D

CALL 693BH CD 3B 69

CALL 693BH - Display prompt and wait for response.

6880

CALL 58C8H CD C8 58

CALL 58C8H - Get user response (Y/N).

6883

JP NZ,67CAH C2 CA 67

If NZ FLAG (user said Yes/retry), JUMP to 67CAH to retry.

6886H - Proceed with Copy/Format Operation

After setup and validation, this section proceeds with the actual copy or format operation. It checks density compatibility and prompts for physical formatting if needed.

6886

LD A,(5997H) 3A 97 59

Load A with command flags from 5997H.

6889

BIT 3,A CB 5F

Test bit 3 - special processing flag.

688B

RET NZ C0

If NZ FLAG (special processing), RETURN to caller.

688C

LD A,(59C7H) 3A C7 59

Load A with disk density flags from 59C7H.

688F

BIT 5,A CB 6F

Test bit 5 - double density flag.

6891

CALL NZ,6751H C4 51 67

If NZ FLAG (double density), CALL 6751H to validate space.

6894

LD HL,6D61H 21 61 6D

Load HL with 6D61H - "Format disk?" prompt message.

6897

CALL 4467H (SYS0) - Display prompt.

689A

CALL 476EH CD 6E 47

CALL 476EH - Get Y/N response from user.

689D

CALL Z,4745H CC 45 47

If Z FLAG (user said Yes), CALL 4745H - confirm operation.

68A0

If NZ FLAG (user cancelled), JUMP to 521AH error/abort.

68A3

LD A,(5997H) 3A 97 59

Load A with command flags from 5997H.

68A6

AND 02H E6 02

Mask with 02H to test track-by-track mode.

68A8

JR Z,68D0H 28 26

If Z FLAG (not track mode), JUMP to 68D0H.

Track-by-track format mode - format each track individually.

68AA

LD DE,0001H 11 01 00

Load DE with 1 - starting track number.

68AD

LD A,D 7A

Load A with D (0).

68AE

ADD A,E 83

Add E to A (result = 1).

68AF

LD C,A 4F

Save result in C.

68B0

JR C,68B6H 38 04

If Carry (overflow), JUMP to 68B6H.

68B2

LD A,(59C8H) 3A C8 59

Load A with total tracks from 59C8H.

68B5

CP C B9

Compare total tracks with current track.

68B6

JP C,5218H DA 18 52

If Carry (past last track), JUMP to 5218H error.

68B9

BIT 1,(IY+91H) FD CB 91 4E

Test bit 1 of (IY+91H) - double-sided flag.

68BD

JR Z,68C0H 28 01

If Z FLAG (single-sided), JUMP to 68C0H.

68BF

INC D 14

Increment D (track count for double-sided).

68C0

LD A,D 7A

Load A with D (side/track offset).

68C1

LD (6AF4H),A 32 F4 6A

Store to 6AF4H - format routine parameter.

68C4

LD (37EFH),A 32 EF 37

Store to 37EFH - FDC data register (for format).

68C7

LD C,18H 0E 18

Load C with 18H (24) - format command parameter.

68C9

CALL 4747H CD 47 47

CALL 4747H - Execute format track operation.

68CC

LD A,D 7A

Load A with D.

68CD

ADD A,E 83

Add E to A.

68CE

JR 6922H 18 52

JUMP to 6922H to continue format.

68D0H - Full Disk Format Mode

Handles full disk format operation, formatting all tracks. Checks for system requirements and double-density support.

68D0

LD A,(59C8H) 3A C8 59

Load A with total tracks from 59C8H.

68D3

LD HL,5996H 21 96 59

Load HL with 5996H - flags address.

68D6

BIT 7,(HL) CB 7E

Test bit 7 - full format flag.

68D8

JR NZ,6922H 20 48

If NZ FLAG (full format), JUMP to 6922H to begin.

68DA

BIT 6,(IY+8CH) FD CB 8C 76

Test bit 6 of (IY+8CH) - double-density capable flag.

68DE

JR Z,6922H 28 42

If Z FLAG (single density only), JUMP to 6922H.

Double-density format setup - configure for double-density operation.

68E0

PUSH IX DD E5

Save IX to stack.

68E2

LD IX,(4399H) DD 2A 99 43

Load IX with pointer from 4399H (system area).

68E6

LD A,01H 3E 01

Load A with 1.

68E8

LD E,(IY+91H) FD 5E 91

Load E with (IY+91H) - density configuration.

68EB

XOR E AB

XOR A with E to toggle density bit.

68EC

AND C1H E6 C1

Mask with C1H to isolate relevant bits.

68EE

LD (IX+07H),A DD 77 07

Store to (IX+07H) - density configuration byte.

68F1

CALL 54D7H CD D7 54

CALL 54D7H - Set up density parameters.

68F4

LD (IX+04H),04H DD 36 04 0A

Store 0AH to (IX+04H) - format parameter. Note: The immediate value appears to be 0AH based on opcode DD 36 04 0A.

68F8

EX (SP),IX DD E3

Exchange IX with value on stack (swap FCB pointers).

68FA

PUSH DE D5

Save DE to stack.

68FB

LD A,01H 3E 01

Load A with 1 - track number to format.

68FD

PUSH BC C5

Save BC to stack.

68FE

CALL 6959H CD 59 69

CALL 6959H - Format track routine.

6901

CALL Z,67AAH CC AA 67

If Z FLAG (format successful), CALL 67AAH - wait/confirm.

6904

POP BC C1

Restore BC from stack.

6905

POP DE D1

Restore DE from stack.

6906

EX (SP),IX DD E3

Swap IX with stack again.

6908

PUSH AF F5

Save AF (flags) to stack.

6909

CALL 54ECH CD EC 54

CALL 54ECH - Clean up density settings.

690C

LD (IX+04H),D DD 72 04

Restore (IX+04H) with D.

690F

CALL 4773H - Additional format cleanup.

6912

EX AF,AF' 08

Switch to alternate AF.

6913

POP AF F1

Restore AF from stack.

6914

POP IX DD E1

Restore IX from stack.

6916

JR NZ,6925H 20 0D

If NZ FLAG (format error), JUMP to 6925H.

6918

EX AF,AF' 08

Switch back to alternate AF.

6919

JR NZ,6925H 20 0A

If NZ FLAG (error in alternate flags), JUMP to 6925H.

691B

CALL 6CAFH CD AF 6C

CALL 6CAFH - Finalize format operation.

691E

LD A,(59C8H) 3A C8 59

Load A with total tracks from 59C8H.

6921

INC A 3C

Increment track count.

6922

CALL 6959H CD 59 69

CALL 6959H - Format remaining tracks.

6925

EI FB

Enable interrupts (format runs with interrupts disabled).

6926

RET Z C8

If Z FLAG (success), RETURN.

6927

CP FFH FE FF

Compare error code with FFH (user abort).

6929

If NZ FLAG (real error), JUMP to 521AH.

692C

JP 5243H C3 43 52

JUMP to 5243H - user abort handler.

692FH - Display Error with Disk Info

Displays an error message followed by disk identification information.

692F

PUSH HL E5

Save HL (message address) to stack.

6930

CALL 4467H (SYS0) - Display error message.

6933

LD HL,6DC2H 21 C2 6D

Load HL with 6DC2H - "Disk:" label message.

6936

CALL 4467H (SYS0) - Display disk label.

6939

POP HL E1

Restore HL from stack.

693A

RET C9

RETURN to caller.

693BH - Display Disk Name and Date Prompt

Displays a prompt message along with the current disk name and date from the sector buffer.

693B

CALL 4467H (SYS0) - Display first message (in HL).

693E

LD HL,6DA8H 21 A8 6D

Load HL with 6DA8H - "Name:" label message.

6941

CALL 4467H (SYS0) - Display name label.

6944

LD HL,42D0H 21 D0 42

Load HL with 42D0H - disk name in sector buffer.

6947

LD B,08H 06 08

Load B with 8 - disk name length.

6949

CALL 5886H CD 86 58

CALL 5886H - Display B bytes from (HL).

694C

LD B,04H 06 04

Load B with 4 - separator/spacing.

694E

CALL 5898H CD 98 58

CALL 5898H - Display B spaces.

6951

LD B,08H 06 08

Load B with 8 - date length.

6953

CALL 5886H CD 86 58

CALL 5886H - Display 8 bytes (date).

6956

JP 5881H C3 81 58

JUMP to 5881H - output carriage return and continue.

6959H - Format Track Initialization

This routine initializes the format track operation. It selects timing parameters based on CPU speed (from system flags at 4311H) and patches self-modifying code locations throughout the format routine. The timing is critical for proper FDC operation across different TRS-80 CPU speeds (1.77MHz, 2.03MHz, 4MHz).

6959

LD (6C75H),A 32 75 6C

Store track count parameter to 6C75H for format operation.

695C

CALL 4773H - Check drive ready status.

695F

RET NZ C0

If NZ FLAG (drive not ready), RETURN with error.

6960

LD A,(4311H) 3A 11 43

Load A with system flags from 4311H. Bits 0-1 indicate CPU speed: 00=1.77MHz, 01=2.03MHz, 10=4MHz.

6963

RLCA 07

Rotate left to position speed bits for table offset calculation.

6964

AND 03H E6 03

Mask to isolate speed indicator (0, 1, or 2).

6966

LD L,1AH 2E 1A

Load L with 26 (1AH) - size of each timing parameter block.

6968

CALL 4C92H (SYS0) - Multiply A * L to get table offset.

696B

LD DE,6CC2H 11 C2 6C

Load DE with 6CC2H - base address of timing parameter tables.

696E

ADD HL,DE 19

Add offset to base - HL now points to correct timing table for CPU speed.

[PATCH TIMING VALUES] - Copy timing values from table to self-modifying code targets.

696F

LD A,(HL) 7E

Load first timing value from table.

6970

LD (6B1CH),A 32 1C 6B

Patch 6B1CH - gap byte count in ID field write.

6973

INC HL 23

Advance to next table entry.

6974

LD (6B83H),A 32 83 6B

Patch 6B83H - same value for sector gap.

6977

LD A,(HL) 7E

Load next timing value.

6978

LD (6AD8H),A 32 D8 6A

Patch 6AD8H - track number byte position.

697B

INC HL 23

Advance table pointer.

697C

LD (6B4DH),A 32 4D 6B

Patch 6B4DH - additional timing target.

697F

LD A,(HL) 7E

Load next timing value.

6980

LD (6B6FH),A 32 6F 6B

Patch 6B6FH - data field fill byte.

6983

INC HL 23

Advance table pointer.

6984

LD A,(HL) 7E

Load next timing value.

6985

LD (6B76H),A 32 76 6B

Patch 6B76H - data field timing.

6988

INC HL 23

Advance table pointer.

6989

LD A,(HL) 7E

Load next timing value.

698A

LD (6B8BH),A 32 8B 6B

Patch 6B8BH - inter-sector gap timing.

698D

INC HL 23

Advance table pointer.

698E

LD A,(HL) 7E

Load next timing value.

698F

LD (6AC8H),A 32 C8 6A

Patch 6AC8H - loop counter value.

6992

INC HL 23

Advance table pointer.

6993

LD A,(HL) 7E

Load next timing value.

6994

LD (6B26H),A 32 26 6B

Patch 6B26H - ID address mark timing.

6997

INC HL 23

Advance table pointer.

6998

LD A,(HL) 7E

Load next timing value.

6999

LD (6B3DH),A 32 3D 6B

Patch 6B3DH - data address mark timing.

699C

INC HL 23

Advance table pointer.

[LOAD 16-BIT TIMING VALUES] - Load word values for more complex timing patches.

699D

LD E,(HL) 5E

Load low byte of timing word.

699E

INC HL 23

Advance pointer.

699F

LD D,(HL) 56

Load high byte - DE now contains timing word.

69A0

INC HL 23

Advance pointer.

69A1

LD C,(HL) 4E

Load low byte of second timing word.

69A2

INC HL 23

Advance pointer.

69A3

LD B,(HL) 46

Load high byte - BC now contains second timing word.

69A4

LD (69DAH),BC ED 43 DA 69

Patch 69DAH with BC - self-modifying LD HL instruction operand.

69A8

INC HL 23

Advance table pointer.

69A9

LD C,(HL) 4E

Load low byte of third timing word.

69AA

INC HL 23

Advance pointer.

69AB

LD B,(HL) 46

Load high byte - BC contains third timing word.

69AC

LD (69F2H),BC ED 43 F2 69

Patch 69F2H with BC.

69B0

INC HL 23

Advance table pointer.

69B1

LD C,(HL) 4E

Load low byte of fourth timing word.

69B2

INC HL 23

Advance pointer.

69B3

LD B,(HL) 46

Load high byte.

69B4

LD (69D6H),BC ED 43 D6 69

Patch 69D6H with BC.

69B8

INC HL 23

Advance table pointer.

69B9

LD A,(HL) 7E

Load next single-byte timing value.

69BA

LD (6A00H),A 32 00 6A

Patch 6A00H - ADD instruction operand.

69BD

INC HL 23

Advance table pointer.

69BE

LD A,(HL) 7E

Load final timing value.

69BF

LD (6A33H),A 32 33 6A

Patch 6A33H - ADD instruction operand.

69C2

INC HL 23

Advance past timing table (HL now points to unused area).

69C3

NOP 00

No operation (padding/alignment).

69C4

NOP 00

No operation.

69C5

NOP 00

No operation.

[INITIALIZE FORMAT VARIABLES] - Clear working variables for format operation.

69C6

XOR A AF

Clear A to zero.

69C7

LD (6A02H),A 32 02 6A

Clear 6A02H - format sector counter.

69CA

LD (6C63H),A 32 63 6C

Clear 6C63H - side flag (0 = front side).

69CD

EX DE,HL EB

Exchange DE and HL (HL now contains timing word from earlier).

69CE

CALL 6CA4H - Get sectors per track into E.

69D1

LD A,E 7B

Load A with sectors per track.

69D2

CALL 4C94H CD 94 4C

CALL 4C94H (SYS0) - Calculate based on sectors per track.

69D5

LD BC,0000H 01 00 00

Load BC with 0. Self-modifying code target at 69D6H - patched with timing value.

69D8

EX DE,HL EB

Exchange DE and HL.

69D9

LD HL,0000H 21 00 00

Load HL with 0. Self-modifying code target at 69DAH - patched with timing value.

69DC

OR A B7

Clear Carry flag.

69DD

SBC HL,DE ED 52

Subtract DE from HL (calculate difference).

69DF

PUSH HL E5

Save result to stack.

69E0

JR NC,69F1H 30 0F

If NC FLAG (no borrow), JUMP to 69F1H.

69E2

ADD HL,HL 29

Double HL (multiply by 2).

69E3

ADD HL,HL 29

Double HL again (multiply by 4).

69E4

ADD HL,BC 09

Add BC to HL.

69E5

JR C,69EEH 38 07

If Carry FLAG (overflow), JUMP to 69EEH.

69E7

POP HL E1

Restore HL from stack.

69E8

LD HL,6D6CH 21 6C 6D

Load HL with 6D6CH - "MOTOR FAST" error message address.

69EB

OR FFH F6 FF

Set A to FFH (error code) and set flags.

69ED

RET C9

RETURN with error - motor speed too fast for format.

69EE

LD HL,0000H 21 00 00

Load HL with 0 (reset for next calculation).

69F1

LD DE,0000H 11 00 00

Load DE with 0. Self-modifying code target at 69F2H - patched with timing value.

69F4

ADD HL,DE 19

Add DE to HL.

69F5

LD (6BCDH),HL 22 CD 6B

Store result to 6BCDH - format timing parameter.

69F8

POP HL E1

Restore HL from stack.

69F9

ADD HL,DE 19

Add DE to HL.

69FA

ADD HL,BC 09

Add BC to HL.

69FB

ADD HL,BC 09

Add BC again.

69FC

LD (6BD6H),HL 22 D6 6B

Store result to 6BD6H - another timing parameter.

69FF

LD A,02H 3E 02

Load A with 2.

6A01

ADD 00H C6 00

Add 0 to A. Self-modifying code target at 6A00H - operand is patched.

6A03

CALL 6CA4H - Get sectors per track.

6A06

CP E BB

Compare A with E (sectors per track).

6A07

JR C,6A0AH 38 01

If Carry FLAG (A < E), JUMP to 6A0AH.

6A09

SUB E 93

Subtract E from A (wrap sector number).

6A0A

LD (6A02H),A 32 02 6A

Store starting sector number to 6A02H.

6A0D

LD (6A02H),A 32 02 6A

Store again (redundant but ensures value is set).

6A10

INC A 3C

Increment A.

6A11

LD D,A 57

Copy to D (sector counter for interleave).

6A12

PUSH DE D5

Save DE to stack.

6A13H - Generate Sector Interleave Table

This routine generates the sector interleave table at 6485H. The interleave pattern determines the physical order of sectors on the track to optimize read performance by allowing time for the system to process data between sequential sector reads.

6A13

LD HL,6485H 21 85 64

Load HL with 6485H - sector interleave table address.

6A16

LD B,E 43

Load B with E (sectors per track) as counter.

6A17

LD (HL),FFH 36 FF

[CLEAR TABLE LOOP] Initialize table entry to FFH (unused marker).

6A19

INC HL 23

Advance to next table entry.

6A1A

DJNZ 6A17H 10 FB

Decrement B, if NZ FLAG, JUMP to 6A17H to continue clearing.

6A1C

LD D,00H 16 00

Initialize D to 0 (physical sector number).

6A1E

LD B,D 42

Initialize B to 0.

6A1F

JR 6A26H 18 05

JUMP to 6A26H to start interleave generation.

6A21

INC C 0C

[FIND NEXT SLOT] Increment C (table position).

6A22

LD A,C 79

Load A with C.

6A23

CP E BB

Compare with E (sectors per track).

6A24

JR C,6A28H 38 02

If Carry (C < sectors), JUMP to 6A28H.

6A26

LD C,00H 0E 00

Wrap C back to 0 (start of table).

6A28

LD HL,6485H 21 85 64

Load HL with 6485H - interleave table base.

6A2B

ADD HL,BC 09

Add BC to get table[C] address.

6A2C

LD A,(HL) 7E

Load current table entry.

6A2D

INC A 3C

Increment (test if FFH - unused slot becomes 00H).

6A2E

JR NZ,6A21H 20 F1

If NZ FLAG (slot already used), JUMP to 6A21H to find next.

6A30

LD (HL),D 72

Store physical sector number D into table slot.

6A31

LD A,C 79

Load A with current position C.

6A32

ADD 02H C6 02

Add interleave factor. Self-modifying target at 6A33H - value patched based on CPU speed.

6A34

CP E BB

Compare with sectors per track.

6A35

JR C,6A38H 38 01

If Carry (within range), JUMP to 6A38H.

6A37

SUB E 93

Wrap position by subtracting sectors per track.

6A38

LD C,A 4F

Update C with new position.

6A39

INC D 14

Increment physical sector number D.

6A3A

LD A,D 7A

Load A with D.

6A3B

CP E BB

Compare with sectors per track.

6A3C

JR C,6A28H 38 EA

If Carry (more sectors to place), JUMP to 6A28H.

[ADJUST INTERLEAVE TABLE] - Post-process table for proper ordering.

6A3E

LD HL,6A02H 21 02 6A

Load HL with 6A02H - starting sector storage.

6A41

LD A,(HL) 7E

Load starting sector.

6A42

ADD A,C 81

Add current position C.

6A43

LD (HL),A 77

Store adjusted value.

6A44

POP DE D1

Restore DE from stack.

6A45

DEC D 15

Decrement D (rotation counter).

6A46

JR Z,6A58H 28 10

If Z FLAG (done rotating), JUMP to 6A58H.

6A48

LD C,E 4B

Load C with E (sectors per track).

6A49

PUSH DE D5

Save DE to stack.

6A4A

LD HL,6484H 21 84 64

Load HL with 6484H (one before table start).

6A4D

ADD HL,BC 09

Add BC to get end of table.

6A4E

LD D,H 54

Copy HL to DE for LDDR destination.

6A4F

LD E,L 5D

DE = end of table.

6A50

DEC BC 0B

Decrement BC (bytes to move).

6A51

LD A,(HL) 7E

Load last entry value.

6A52

DEC HL 2B

Move source back one position.

6A53

LDDR ED B8

Block copy downward (rotate table right).

6A55

LD (DE),A 12

Store saved last entry at first position.

6A56

JR 6A44H 18 EC

JUMP to 6A44H to continue rotation.

6A58H - Adjust Sector Numbers for Base

Adjusts sector numbers in the interleave table if the disk format uses 1-based sector numbering (some formats start sectors at 1 instead of 0).

6A58

LD A,(4311H) 3A 11 43

Load A with system flags from 4311H.

6A5B

BIT 4,A CB 67

Test bit 4 - 1-based sector numbering flag.

6A5D

JR Z,6A67H 28 08

If Z FLAG (0-based), JUMP to 6A67H (no adjustment needed).

6A5F

LD B,E 43

Load B with E (sectors per track) as counter.

6A60

LD HL,6485H 21 85 64

Load HL with 6485H - interleave table address.

6A63

INC (HL) 34

[INCREMENT LOOP] Increment table entry (add 1 to sector number).

6A64

INC HL 23

Advance to next entry.

6A65

DJNZ 6A63H 10 FC

Decrement B, if NZ FLAG, JUMP to 6A63H.

6A67H - Format Track Main Entry

This is the main entry point for formatting a single track. It sets up the FDC registers, positions the head, and initiates the WRITE TRACK command. The track formatting writes ID fields, data fields, gaps, and sync patterns in the proper sequence.

6A67

LD A,0AH 3E 0A

Load A with 10 (0AH) - retry counter for format operation.

6A69

LD (6C95H),A 32 95 6C

Store retry count to 6C95H.

6A6C

CALL 4773H - Select drive and check ready status.

6A6F

RET NZ C0

If NZ FLAG (drive error), RETURN.

6A70

CALL 5733H CD 33 57

CALL 5733H - Seek to track (track number in FDC track register).

6A73

LD HL,4309H 21 09 43

Load HL with 4309H - FDC control flags address.

6A76

LD B,(IY+91H) FD 46 91

Load B with density/side flags from (IY+91H).

6A79

LD A,B 78

Copy flags to A.

6A7A

AND 40H E6 40

Mask to isolate double-density bit (bit 6).

6A7C

JR Z,6A87H 28 09

If Z FLAG (single density), JUMP to 6A87H.

6A7E

LD A,(6C63H) 3A 63 6C

Load A with side flag from 6C63H.

6A81

AND 01HAND 00000001 E6 01

Mask to bit 0 (side select).

6A83

JR Z,6A87H 28 02

If Z FLAG (side 0), JUMP to 6A87H.

6A85

SET 3,(HL) CB DE

Set bit 3 of (HL) - enable side 1 select in control byte.

6A87

LD (6AFCH),A 32 FC 6A

Store side/density flags to 6AFCH (self-mod target).

6A8A

CALL 4767H CD 67 47

CALL 4767H - Wait for drive motor and head settle.

6A8D

CALL 4750H CD 50 47

CALL 4750H - Wait for index pulse (start of track).

6A90

LD DE,37EFH 11 EF 37

Load DE with 37EFH - FDC Data Register address.

6A93

LD HL,37ECH 21 EC 37

Load HL with 37ECH - FDC Command/Status Register address.

6A96

LD BC,6485H 01 85 64

Load BC with 6485H - sector interleave table address.

6A99

PUSH HL E5

Save FDC status register address.

6A9A

PUSH DE D5

Save FDC data register address.

6A9B

EXX D9

Switch to alternate registers.

6A9C

CALL 6CA4H - Get sectors per track into E.

6A9F

LD C,E 4B

Copy sectors per track to C (sector counter).

6AA0

POP DE D1

Restore DE (37EFH - FDC data register).

6AA1

POP HL E1

Restore HL (37ECH - FDC status register).

6AA2

DI F3

Disable interrupts - critical timing section begins.

6AA3

CALL 47E3H CD E3 47

CALL 47E3H - Wait for FDC ready.

6AA6

LD (HL),F4H 36 F4

Write F4H to FDC - WRITE TRACK command.

WD 1771 FDC Command Code: F4H (11110100)
Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0	Function
1	1	1	1	0	1	0	0	Command=Write Track (Format)

6AA8

CALL 47E3H CD E3 47

CALL 47E3H - Wait for FDC to accept command.

6AAB

LD A,01H 3E 01

Load A with 1 - initial DRQ check value.

6AAD

EX AF,AF' 08

Save A to alternate AF (used for status checking in timing loops).

6AAE

INC C 0C

Increment sector counter (adjust for loop logic).

6AAF

JP 6B82H C3 82 6B

JUMP to 6B82H - enter main format loop at gap writing section.

6AB2H - Format Track: Write Sector ID Field

This section writes the sector ID field during formatting. The timing is critical - the code uses EX AF,AF' to quickly switch between checking FDC status (DRQ bit) and writing data bytes. The pattern: check status, wait for DRQ, switch registers, write byte, repeat.

6AB2

EX AF,AF' 08

[WRITE ID SYNC] Switch to alternate A (status check value).

6AB3

CP (HL) BE

Compare A with FDC status register - wait for DRQ.

6AB4

JR Z,6AB3H 28 FD

If Z FLAG (DRQ not set), loop waiting.

6AB6

EX AF,AF' 08

Switch back to primary A (data byte).

6AB7

LD (DE),A 12

Write byte to FDC data register.

6AB8

EX AF,AF' 08

[WRITE SYNC BYTES LOOP] Switch to status check.

6AB9

CP (HL) BE

Wait for DRQ.

6ABA

JR Z,6AB9H 28 FD

If Z FLAG, keep waiting.

6ABC

EX AF,AF' 08

Switch to data byte.

6ABD

LD (DE),A 12

Write sync byte to FDC.

6ABE

DJNZ 6AB8H 10 F8

Decrement B, if NZ FLAG, continue writing sync bytes.

6AC0

XOR A AF

Clear A to 00H (gap byte value).

6AC1

EX AF,AF' 08

Switch to status check.

6AC2

CP (HL) BE

Wait for DRQ.

6AC3

JR Z,6AC2H 28 FD

If Z FLAG, keep waiting.

6AC5

EX AF,AF' 08

Switch to data (00H).

6AC6

LD (DE),A 12

Write gap byte.

6AC7

LD B,01H 06 01

Load B with count. Self-mod target at 6AC8H - patched with timing value.

6AC9

EX AF,AF' 08

[WRITE GAP BYTES] Status check.

6ACA

CP (HL) BE

Wait for DRQ.

6ACB

JR Z,6ACAH 28 FD

If Z FLAG, keep waiting.

6ACD

EX AF,AF' 08

Switch to data.

6ACE

LD (DE),A 12

Write gap byte.

6ACF

DJNZ 6AC9H 10 F8

Decrement B, continue if more gap bytes.

6AD1

EX AF,AF' 08

Status check.

6AD2

CP (HL) BE

Wait for DRQ.

6AD3

JR Z,6AD2H 28 FD

If Z FLAG, keep waiting.

6AD5

EX AF,AF' 08

Switch to data.

6AD6

LD (DE),A 12

Write byte.

6AD7

LD A,00H 3E 00

Load track number. Self-mod target at 6AD8H - patched with actual track.

[WRITE ID ADDRESS MARK AND TRACK/HEAD/SECTOR]

6AD9

EX AF,AF' 08

Status check.

6ADA

CP (HL) BE

Wait for DRQ.

6ADB

JR Z,6ADAH 28 FD

If Z FLAG, keep waiting.

6ADD

EX AF,AF' 08

Switch to data (track number).

6ADE

LD (DE),A 12

Write track number to ID field.

6ADF

EX AF,AF' 08

Status check.

6AE0

CP (HL) BE

Wait for DRQ.

6AE1

JR Z,6AE0H 28 FD

If Z FLAG, keep waiting.

6AE3

EX AF,AF' 08

Switch to data.

6AE4

LD (DE),A 12

Write track number again (or head number).

6AE5

EX AF,AF' 08

Status check.

6AE6

CP (HL) BE

Wait for DRQ.

6AE7

JR Z,6AE6H 28 FD

If Z FLAG, keep waiting.

6AE9

EX AF,AF' 08

Switch to data.

6AEA

LD (DE),A 12

Write byte.

6AEB

LD A,FEH 3E FE

Load A with FEH - ID Address Mark for single density.

6AED

EX AF,AF' 08

Status check.

6AEE

CP (HL) BE

Wait for DRQ.

6AEF

JR Z,6AEEH 28 FD

If Z FLAG, keep waiting.

6AF1

EX AF,AF' 08

Switch to data (FEH).

6AF2

LD (DE),A 12

Write ID Address Mark.

6AF3

LD A,00H 3E 00

Load track number. Self-mod target at 6AF4H.

6AF5

EX AF,AF' 08

Status check.

6AF6

CP (HL) BE

Wait for DRQ.

6AF7

JR Z,6AF6H 28 FD

If Z FLAG, keep waiting.

6AF9

EX AF,AF' 08

Switch to data.

6AFA

LD (DE),A 12

Write track number in ID field.

6AFB

LD A,00H 3E 00

Load head/side. Self-mod target at 6AFCH.

6AFD

EX AF,AF' 08

Status check.

6AFE

CP (HL) BE

Wait for DRQ.

6AFF

JR Z,6AFEH 28 FD

If Z FLAG, keep waiting.

6B01

EX AF,AF' 08

Switch to data.

6B02

LD (DE),A 12

Write head/side number in ID field.

6B03

EXX D9

Switch to alternate register set.

6B04

LD A,(BC) 0A

Load sector number from interleave table (BC points to table).

6B05

EX AF,AF' 08

Status check (using alternate' A).

6B06

CP (HL) BE

Wait for DRQ.

6B07

JR Z,6B06H 28 FD

If Z FLAG, keep waiting.

6B09

EX AF,AF' 08

Switch to sector number.

6B0A

LD (DE),A 12

Write sector number to ID field.

6B0B

LD A,01H 3E 01

Load A with 1 - sector size code (256 bytes).

6B0D

EX AF,AF' 08

Status check.

6B0E

CP (HL) BE

Wait for DRQ.

6B0F

JR Z,6B0EH 28 FD

If Z FLAG, keep waiting.

6B11

EX AF,AF' 08

Switch to data.

6B12

LD (DE),A 12

Write sector size code.

6B13

LD A,F7H 3E F7

Load A with F7H - CRC generation command for FDC.

6B15

EX AF,AF' 08

Status check.

6B16

CP (HL) BE

Wait for DRQ.

6B17

JR Z,6B16H 28 FD

If Z FLAG, keep waiting.

6B19

EX AF,AF' 08

Switch to data.

6B1A

LD (DE),A 12

Write F7H - FDC generates CRC bytes.

6B1B

LD A,FFH 3E FF

Load gap byte. Self-mod target at 6B1CH.

6B1D

EX AF,AF' 08

Status check.

6B1E

CP (HL) BE

Wait for DRQ.

6B1F

JR Z,6B1EH 28 FD

If Z FLAG, keep waiting.

6B21

EX AF,AF' 08

Switch to data.

6B22

LD (DE),A 12

Write gap byte after ID CRC.

6B23

INC BC 03

Advance interleave table pointer.

6B24

EXX D9

Switch back to primary registers.

6B25

LD B,0AH 06 0A

Load gap byte count. Self-mod target at 6B26H.

6B27H - Format Track: Write Data Field

This section writes the data field for each sector - the gap before data, data address mark, 256 bytes of data (E5H fill pattern), and CRC.

6B27

EX AF,AF' 08

[WRITE GAP 2] Status check.

6B28

CP (HL) BE

Wait for DRQ.

6B29

JR Z,6B28H 28 FD

If Z FLAG, keep waiting.

6B2B

EX AF,AF' 08

Switch to data.

6B2C

LD (DE),A 12

Write gap byte.

6B2D

EX AF,AF' 08

Status check.

6B2E

CP (HL) BE

Wait for DRQ.

6B2F

JR Z,6B2EH 28 FD

If Z FLAG, keep waiting.

6B31

EX AF,AF' 08

Switch to data.

6B32

LD (DE),A 12

Write gap byte.

6B33

DJNZ 6B2DH 10 F8

Decrement B, continue gap writing.

6B35

XOR A AF

Clear A to 00H (sync bytes).

6B36

EX AF,AF' 08

Status check.

6B37

CP (HL) BE

Wait for DRQ.

6B38

JR Z,6B37H 28 FD

If Z FLAG, keep waiting.

6B3A

EX AF,AF' 08

Switch to data (00H).

6B3B

LD (DE),A 12

Write sync byte.

6B3C

LD B,04H 06 04

Load sync byte count. Self-mod target at 6B3DH.

6B3E

EX AF,AF' 08

[WRITE DATA SYNC]

6B3F

CP (HL) BE

Wait for DRQ.

6B40

JR Z,6B3FH 28 FD

If Z FLAG, keep waiting.

6B42

EX AF,AF' 08

Switch to data.

6B43

LD (DE),A 12

Write sync byte.

6B44

DJNZ 6B3EH 10 F8

Decrement B, continue sync writing.

6B46

EX AF,AF' 08

Status check.

6B47

CP (HL) BE

Wait for DRQ.

6B48

JR Z,6B47H 28 FD

If Z FLAG, keep waiting.

6B4A

EX AF,AF' 08

Switch to data.

6B4B

LD (DE),A 12

Write byte.

6B4C

LD A,00H 3E 00

Load data mark. Self-mod target at 6B4DH.

6B4E

EX AF,AF' 08

Status check.

6B4F

CP (HL) BE

Wait for DRQ.

6B50

JR Z,6B4FH 28 FD

If Z FLAG, keep waiting.

6B52

EX AF,AF' 08

Switch to data.

6B53

LD (DE),A 12

Write byte.

6B54

EX AF,AF' 08

Status check.

6B55

CP (HL) BE

Wait for DRQ.

6B56

JR Z,6B55H 28 FD

If Z FLAG, keep waiting.

6B58

EX AF,AF' 08

Switch to data.

6B59

LD (DE),A 12

Write byte.

6B5A

EX AF,AF' 08

Status check.

6B5B

CP (HL) BE

Wait for DRQ.

6B5C

JR Z,6B5BH 28 FD

If Z FLAG, keep waiting.

6B5E

EX AF,AF' 08

Switch to data.

6B5F

LD (DE),A 12

Write byte.

6B60

LD B,80H 06 80

Load B with 128 (80H) - half of 256-byte sector.

[WRITE 256 DATA BYTES] - Write sector data (E5H fill pattern, 256 bytes total).

6B62

EX AF,AF' 08

Status check.

6B63

CP (HL) BE

Wait for DRQ.

6B64

JR Z,6B63H 28 FD

If Z FLAG, keep waiting.

6B66

EX DE,HL EB

Swap DE/HL (now HL=data reg, DE=status reg).

6B67

LD (HL),FBH 36 FB

Write FBH - Data Address Mark.

6B69

EX DE,HL EB

Swap back.

6B6A

CP (HL) BE

Wait for DRQ.

6B6B

JR Z,6B6AH 28 FD

If Z FLAG, keep waiting.

6B6D

EX DE,HL EB

Swap DE/HL.

6B6E

LD (HL),E5H 36 E5

Write E5H - data fill byte. Self-mod target at 6B6FH.

6B70

EX DE,HL EB

Swap back.

6B71

CP (HL) BE

Wait for DRQ.

6B72

JR Z,6B71H 28 FD

If Z FLAG, keep waiting.

6B74

EX DE,HL EB

Swap DE/HL.

6B75

LD (HL),E5H 36 E5

Write another E5H. Self-mod target at 6B76H.

6B77

EX DE,HL EB

Swap back.

6B78

DJNZ 6B6AH 10 F0

Decrement B, continue writing data bytes (128 iterations × 2 bytes = 256).

6B7A

CP (HL) BE

Wait for DRQ.

6B7B

JR Z,6B7AH 28 FD

If Z FLAG, keep waiting.

6B7D

EX DE,HL EB

Swap DE/HL.

6B7E

LD (HL),F7H 36 F7

Write F7H - CRC generation command.

6B80

EX DE,HL EB

Swap back.

6B81

EX AF,AF' 08

Switch to data register A.

6B82H - Format Track: Write Inter-Sector Gap

Writes the gap between sectors (Gap 3). After completing all sectors, the routine continues filling the track with gap bytes until the next index pulse.

6B82

LD A,FFH 3E FF

Load gap byte FFH. Self-mod target at 6B83H.

6B84

EX AF,AF' 08

Status check.

6B85

CP (HL) BE

Wait for DRQ.

6B86

JR Z,6B85H 28 FD

If Z FLAG, keep waiting.

6B88

EX AF,AF' 08

Switch to data.

6B89

LD (DE),A 12

Write gap byte.

6B8A

LD B,0AH 06 0A

Load gap count. Self-mod target at 6B8BH.

6B8C

DEC C 0D

Decrement sector counter C.

6B8D

JP NZ,6AB2H C2 B2 6A

If NZ FLAG (more sectors), JUMP to 6AB2H to write next sector.

[FILL REMAINDER OF TRACK] - All sectors written, fill to index pulse.

6B90

LD BC,0001H 01 01 00

Initialize byte counter BC = 1.

6B93

EX AF,AF' 08

[FILL LOOP] Status check.

6B94

CP (HL) BE

Wait for DRQ.

6B95

JR Z,6B94H 28 FD

If Z FLAG, keep waiting.

6B97

EX AF,AF' 08

Switch to data.

6B98

LD (DE),A 12

Write gap byte.

6B99

INC BC 03

Increment byte counter.

6B9A

NOP 00

Timing padding.

6B9B

BIT 1,(HL) CB 4E

Test DRQ bit of FDC status.

6B9D

JP NZ,6B98H C2 98 6B

If NZ FLAG (DRQ set), write another byte.

6BA0

BIT 1,(HL) CB 4E

Test DRQ again.

6BA2

JP NZ,6B98H C2 98 6B

If NZ FLAG, write another byte.

6BA5

BIT 1,(HL) CB 4E

Test DRQ third time.

6BA7

JR NZ,6B98H 20 EF

If NZ FLAG, write another byte.

6BA9

BIT 0,(HL) CB 46

Test BUSY bit of FDC status.

6BAB

JR Z,6BB5H 28 08

If Z FLAG (not busy = format complete), JUMP to 6BB5H.

6BAD

BIT 1,(HL) CB 4E

Test DRQ while still busy.

6BAF

JR NZ,6B98H 20 E7

If NZ FLAG (DRQ set), write byte.

6BB1

BIT 7,(HL) CB 7E

Test NOT READY bit.

6BB3

JR Z,6B9BH 28 E6

If Z FLAG (drive ready), continue polling.

[FORMAT COMPLETE] - Track formatting finished.

6BB5

LD A,(HL) 7E

Read final FDC status.

6BB6

LD (HL),D0H 36 D0

Write D0H - FORCE INTERRUPT to terminate operation.

6BB8H - Format Track Verification

After writing the track, this section verifies the format by reading back sectors and checking for errors. It handles retry logic and reports format failures.

6BB8

LD H,B 60

Copy B to H (save counter high byte).

6BB9

LD L,C 69

Copy C to L - HL now contains byte count written.

6BBA

LD B,A 47

Save FDC status in B.

6BBB

CALL 4767H CD 67 47

CALL 4767H - Wait for motor/head settle.

6BBE

LD A,(5996H) 3A 96 59

Load operation flags from 5996H.

6BC1

BIT 7,A CB 7F

Test bit 7 - skip verify flag.

6BC3

JP NZ,6C5CH C2 5C 6C

If NZ FLAG (skip verify), JUMP to 6C5CH.

6BC6

LD A,B 78

Restore FDC status to A.

6BC7

AND FCH E6 FC

Mask to isolate error bits (ignore BUSY and DRQ).

6BC9

JP NZ,6C89H C2 89 6C

If NZ FLAG (format error), JUMP to 6C89H error handler.

6BCC

LD BC,0000H 01 00 00

Load expected byte count. Self-mod target at 6BCDH.

6BCF

OR A B7

Clear Carry flag.

6BD0

SBC HL,BC ED 42

Subtract expected from actual byte count.

6BD2

JP C,6C7DH DA 7D 6C

If Carry (too few bytes), JUMP to 6C7DH - "MOTOR FAST" error.

6BD5

LD BC,007DH 01 7D 00

Load tolerance value. Self-mod target at 6BD6H.

6BD8

OR A B7

Clear Carry flag.

6BD9

SBC HL,BC ED 42

Check if within tolerance.

6BDB

JP NC,6C82H D2 82 6C

If NC FLAG (too many bytes), JUMP to 6C82H - "MOTOR SLOW" error.

[VERIFY FORMAT BY READING SECTORS]

6BDE

LD A,88H 3E 88

Load 88H - READ SECTOR command for verification.

6BE0

LD (46C4H),A 32 C4 46

Store command to 46C4H for sector read routine.

6BE3

LD HL,(4649H) 2A 49 46

Load current buffer pointer from 4649H.

6BE6

LD (46FCH),HL 22 FC 46

Store to 46FCH for read operation.

6BE9

LD HL,6485H 21 85 64

Load HL with 6485H - interleave table address.

6BEC

CALL 6CA4H - Get sectors per track.

6BEF

INC HL 23

[VERIFY LOOP] Advance to next sector in table.

6BF0

LD A,(HL) 7E

Load sector number from interleave table.

6BF1

LD (37EEH),A 32 EE 37

Write sector number to FDC Sector Register.

6BF4

LD A,(37EDH) 3A ED 37

Read current track from FDC Track Register.

6BF7

PUSH HL E5

Save interleave table pointer.

6BF8

LD HL,471AH 21 1A 47

Load HL with 471AH - routine address to patch.

6BFB

LD D,(HL) 56

Save original byte.

6BFC

PUSH DE D5

Save original byte and track.

6BFD

PUSH HL E5

Save patch address.

6BFE

LD (HL),C9H 36 C9

Patch with RET instruction (skip normal processing).

6C00

PUSH AF F5

Save track number.

6C01

LD A,(6AF4H) 3A F4 6A

Load side/track info from 6AF4H.

6C04

LD (37EDH),A 32 ED 37

Write to FDC Track Register.

6C07

LD BC,0000H 01 00 00

Clear BC for read operation.

6C0A

CALL 46BDH CD BD 46

CALL 46BDH - Read sector for verification.

6C0D

LD B,A 47

Save read status in B.

6C0E

POP AF F1

Restore track number.

6C0F

LD (37EDH),A 32 ED 37

Restore FDC Track Register.

6C12

POP HL E1

Restore patch address.

6C13

POP DE D1

Restore original byte.

6C14

LD (HL),D 72

Restore original instruction.

6C15

POP HL E1

Restore interleave table pointer.

6C16

LD A,B 78

Load read status to A.

6C17

AND 9CH E6 9C

Mask to isolate significant error bits.

6C19

JR Z,6C51H 28 36

If Z FLAG (no errors), JUMP to 6C51H to verify next sector.

[VERIFY ERROR - RETRY]

6C1B

LD HL,6C95H 21 95 6C

Load HL with 6C95H - retry counter address.

6C1E

DEC (HL) 35

Decrement retry counter.

6C1F

JP NZ,6A6CH C2 6C 6A

If NZ FLAG (retries remaining), JUMP to 6A6CH to reformat track.

[FORMAT FAILED - ALL RETRIES EXHAUSTED]

6C22

EI FB

Enable interrupts.

6C23

LD HL,6EABH 21 AB 6E

Load HL with 6EABH - "FRONT" message address.

6C26

LD A,(6C63H) 3A 63 6C

Load side flag from 6C63H.

6C29

OR A B7

Test if side 0.

6C2A

JR Z,6C2FH 28 03

If Z FLAG (side 0), JUMP to 6C2FH.

6C2C

LD HL,6EB0H 21 B0 6E

Load HL with 6EB0H - " BACK" message address.

6C2F

LD DE,6E96H 11 96 6E

Load DE with 6E96H - destination for side text.

6C32

LD BC,0005H 01 05 00

Load BC with 5 - length of side text.

6C35

LDIR ED B0

Copy side text to message buffer.

6C37

LD HL,6E89H 21 89 6E

Load HL with 6E89H - "CAN'T FORMAT" message.

6C3A

CALL 4467H (SYS0) - Display error message.

6C3D

LD A,(6AF4H) 3A F4 6A

Load track number from 6AF4H.

6C40

LD E,A 5F

Copy to E.

6C41

LD D,00H 16 00

Clear D (DE = track number).

6C43

CALL 5909H CD 09 59

CALL 5909H - Display track number.

6C46

CALL 5881H - Output carriage return.

6C49

CALL 58C8H CD C8 58

CALL 58C8H - Wait for user keypress.

6C4C

JP NZ,6A67H C2 67 6A

If NZ FLAG (user wants retry), JUMP to 6A67H.

6C4F

JR 6C5CH 18 0B

JUMP to 6C5CH - continue to next track.

[CONTINUE VERIFICATION]

6C51

DEC E 1D

Decrement sector counter E.

6C52

LD A,01H 3E 01

Load A with 1 for comparison.

6C54

CP E BB

Compare with remaining sectors.

6C55

JR C,6BEFH 38 98

If Carry (more sectors), JUMP to 6BEFH to verify next.

6C57

LD A,(6485H) 3A 85 64

Load first sector from interleave table.

6C5A

JR Z,6BF1H 28 95

If Z FLAG (last sector), verify sector 0.

6C5CH - Format Next Side/Track

After completing one side of a track, this section handles double-sided disks by formatting the back side, then advances to the next track.

6C5C

BIT 6,(IY+91H) FD CB 91 76

Test bit 6 of (IY+91H) - double-sided flag.

6C60

JR Z,6C6FH 28 0D

If Z FLAG (single-sided), JUMP to 6C6FH.

6C62

LD A,00H 3E 00

Load current side. Self-mod target at 6C63H.

6C64

XOR 01H EE 01

Toggle side bit (0→1 or 1→0).

6C66

LD (6C63H),A 32 63 6C

Store new side value.

6C69

JR Z,6C6FH 28 04

If Z FLAG (back to side 0), JUMP to 6C6FH - advance track.

6C6B

XOR A AF

Clear A.

6C6C

JP 6A01H C3 01 6A

JUMP to 6A01H - format side 1 of same track.

[ADVANCE TO NEXT TRACK]

6C6F

LD HL,6AF4H 21 F4 6A

Load HL with 6AF4H - track number storage.

6C72

INC (HL) 34

Increment track number.

6C73

LD A,(HL) 7E

Load new track number.

6C74

CP 23H FE 23

Compare with 35 (23H). Self-mod target at 6C75H - patched with max track.

6C76

RET Z C8

If Z FLAG (all tracks done), RETURN - format complete.

6C77

CALL 6CAFH CD AF 6C

CALL 6CAFH - Motor delay between tracks.

6C7A

JP 69FFH C3 FF 69

JUMP to 69FFH - format next track.

6C7DH - Motor Speed Errors

Error handlers for motor speed problems detected during format.

6C7D

LD HL,6D6CH 21 6C 6D

Load HL with 6D6CH - "MOTOR FAST" message address.

6C80

JR 6C85H 18 03

JUMP to 6C85H to set error code.

6C82

LD HL,6D77H 21 77 6D

Load HL with 6D77H - "MOTOR SLOW" message address.

6C85

LD B,FFH 06 FF

Load B with FFH - fatal error code.

6C87

JR 6C94H 18 0B

JUMP to 6C94H to process error.

6C89H - FDC Error Handler

Handles FDC errors during format by analyzing the status bits and determining retry behavior.

6C89

LD B,11H 06 11

Initialize error bit counter.

6C8B

DEC B 05

[FIND ERROR BIT] Decrement counter.

6C8C

RLCA 07

Rotate A left to test next bit.

6C8D

JR NC,6C8BH 30 FC

If NC FLAG (bit not set), continue searching.

6C8F

LD A,B 78

Load error bit number to A.

6C90

CP 0FH FE 0F

Compare with 15 (write protect error).

6C92

JR Z,6CA2H 28 0E

If Z FLAG (write protected), JUMP to 6CA2H - fatal error.

6C94

LD A,00H 3E 00

Load retry count. Self-mod target at 6C95H.

6C96

DEC A 3D

Decrement retry counter.

6C97

LD (6C95H),A 32 95 6C

Store updated count.

6C9A

JP NZ,6A6CH C2 6C 6A

If NZ FLAG (retries remaining), JUMP to 6A6CH to retry.

6C9D

LD A,B 78

Load error code to A.

6C9E

CP 0BH FE 0B

Compare with specific error.

6CA0

JR Z,6C22H 28 80

If Z FLAG, JUMP to 6C22H - display error.

6CA2

OR A B7

Set flags based on A (error code in A).

6CA3

RET C9

RETURN with error code in A.

6CA4H - Get Sectors Per Track

Utility routine to get the sectors per track value, adjusting for double-sided disks.

6CA4

LD E,(IY+8EH) FD 5E 8E

Load E with sectors per track from (IY+8EH).

6CA7

BIT 6,(IY+91H) FD CB 91 76

Test bit 6 - double-sided flag.

6CAB

RET Z C8

If Z FLAG (single-sided), RETURN with E unchanged.

6CAC

SRL E CB 3B

Shift E right (divide by 2 for double-sided).

6CAE

RET C9

RETURN with adjusted sector count.

6CAFH - Motor Step Delay

Provides timing delay for drive motor stepping between tracks.

6CAF

LD A,(4311H) 3A 11 43

Load system flags from 4311H.

6CB2

BIT 2,A CB 57

Test bit 2 - extra delay needed flag.

6CB4

CALL NZ,6CB7H C4 B7 6C

If NZ FLAG, CALL 6CB7H to add extra delay (recursive).

6CB7

LD BC,0100H 01 00 01

Load delay counter.

6CBA

CALL 4CEDH CD ED 4C

CALL 4CEDH (SYS0) - Delay loop.

6CBD

LD C,58H 0E 58

Load C with 58H (88) - step rate command.

6CBF

JP 4747H C3 47 47

JUMP to 4747H - Execute step command.

6CC2H - Format Timing Parameter Tables

These tables contain CPU speed-dependent timing parameters for the format routine. Each 26-byte (1AH) block contains values for a different CPU speed: 1.77MHz, 2.03MHz, and 4MHz. The values are copied to self-modifying code locations at runtime.

6CC2

DEFB FFH, 00H, E5H, E5H, 09H, 01H, 09H, 01H FF 00 E5 E5 09 01 09 01

Table 1 (1.77MHz) - Timing bytes 0-7.

6CCA

DEFB 2CH, 01H, ECH, 0BH, 0BH, 00H 2C 01 EC 0B 0B 00

Timing bytes 8-13.

6CD0

DEFB 3EH, 00H, 02H, 02H, 00H, 00H 3E 00 02 02 00 00

Timing bytes 14-19.

6CD6

DEFB 00H, 00H, 00H, 00H, 00H, 00H 00 00 00 00 00 00

Timing bytes 20-25 (padding).

6CDC

DEFB FFH, 00H, E5H, E5H, 08H, 01H, 09H, 01H FF 00 E5 E5 08 01 09 01

Table 2 (2.03MHz) - Timing bytes 0-7.

6CE4

DEFB 2BH, 01H, E6H, 13H, 0AH, 00H 2B 01 E6 13 0A 00

Timing bytes 8-13.

6CEA

DEFB 68H, 00H, 04H, 03H, 00H, 00H 68 00 04 03 00 00

Timing bytes 14-19.

6CF0

DEFB 00H, 00H, 00H, 00H, 00H, 00H 00 00 00 00 00 00

Timing bytes 20-25 (padding).

6CF6

DEFB 4EH, F5H, E5H, E5H, 0EH, 06H, 14H, 0AH 4E F5 E5 E5 0E 06 14 0A

Table 3 (4MHz) - Timing bytes 0-7.

6CFE

DEFB 4AH, 01H, DDH, 17H, 10H, 00H 4A 01 DD 17 10 00

Timing bytes 8-13.

6D04

DEFB 7DH, 00H, 04H, 03H, 00H, 00H 7D 00 04 03 00 00

Timing bytes 14-19.

6D0A

DEFB 00H, 00H, 00H, 00H, 00H, 00H 00 00 00 00 00 00

Timing bytes 20-25 (padding).

6D10

DEFB 4EH, F5H, E5H, E5H, 13H, 0AH, 14H, 0AH 4E F5 E5 E5 13 0A 14 0A

Table 4 (alternate 4MHz) - Timing bytes 0-7.

6D18

DEFB 53H, 01H, BAH, 27H, 26H, 00H 53 01 BA 27 26 00

Timing bytes 8-13.

6D1E

DEFB D0H, 00H, 05H, 04H, 00H, 00H D0 00 05 04 00 00

Timing bytes 14-19.

6D24

DEFS 3AH (58 bytes of 00H)

Reserved/unused space (filled with 00H).

6D5EH - Message Strings

ASCII message strings used by the FORMAT and COPY commands. Strings are terminated with 0DH (carriage return) or 03H (ETX). Control codes: 1CH=home cursor, 1FH=cursor down.

6D5E

DEFB 1CH, 1FH, 03H 1C 1F 03

Cursor control sequence.

6D61

DEFM 'FORMATTING' 46 4F 52 4D 41 54 54 49 4E 47

String: "FORMATTING"

6D6B

DEFB 0DH 0D

Carriage return terminator.

6D6C

DEFM 'MOTOR FAST' 4D 4F 54 4F 52 20 46 41 53 54

String: "MOTOR FAST"

6D76

DEFB 0DH 0D

Carriage return terminator.

6D77

DEFM 'MOTOR SLOW' 4D 4F 54 4F 52 20 53 4C 4F 57

String: "MOTOR SLOW"

6D81

DEFB 0DH 0D

Carriage return terminator.

6D82

DEFM 'DISKETTE HAS DATA' 44 49 53 4B 45 54 54 45 20 48 41 53 20 44 41 54 41

String: "DISKETTE HAS DATA"

6D93

DEFB 0DH 0D

Carriage return terminator.

6D94

DEFM 'UNREADABLE DISKETTE' 55 4E 52 45 41 44 41 42 4C 45 20 44 49 53 4B 45 54 54 45

String: "UNREADABLE DISKETTE"

6DA7

DEFB 0DH 0D

Carriage return terminator.

6DA8

DEFM 'DISKETTE OLD NAME/DATE = ' 44 49 53 4B 45 54 54 45 20 ...

String: "DISKETTE OLD NAME/DATE = "

6DC1

DEFB 03H 03

ETX terminator.

6DC2

DEFM 'DISKETTE NAME MISMATCH' 44 49 53 4B 45 54 54 45 20 4E 41 4D 45 ...

String: "DISKETTE NAME MISMATCH"

6DD9

DEFB 0AH, 0DH 0A 0D

Line feed + carriage return.

6DDA

DEFM 'INITIALIZING SYSTEM DATA' 49 4E 49 54 49 41 4C 49 5A 49 4E 47 ...

String: "INITIALIZING SYSTEM DATA"

6DF2

DEFB 0DH 0D

Carriage return terminator.

6DF3

DEFM 'STARTING DISKETTE FORMAT' 53 54 41 52 54 49 4E 47 ...

String: "STARTING DISKETTE FORMAT"

6E0BH

DEFB 0DH 0D

Carriage return terminator.

6E0C

DEFM 'STARTING DISKETTE COPY' 53 54 41 52 54 49 4E 47 ...

String: "STARTING DISKETTE COPY"

6E22

DEFB 0DH 0D

Carriage return terminator.

6E23

DEFM 'ARE SYSTEM AND THE SAME DISKETTE?' 41 52 45 20 53 59 53 54 45 4D ...

String: "ARE SYSTEM AND THE SAME DISKETTE?"

6E45

DEFB 03H 03

ETX terminator.

6E46

DEFM 'FORMAT DISKETTE?' 46 4F 52 4D 41 54 ...

String: "FORMAT DISKETTE?"

6E56

DEFB 03H 03

ETX terminator.

6E57

DEFM 'EITHER BAD PARAMETER OR CONFLICT WITH PDRIVE DATA' 45 49 54 48 45 52 ...

String: "EITHER BAD PARAMETER OR CONFLICT WITH PDRIVE DATA"

6E88

DEFB 0DH 0D

Carriage return terminator.

6E89

DEFM "CAN'T FORMAT" 43 41 4E 27 54 20 46 4F 52 4D 41 54

String: "CAN'T FORMAT"

6E95

DEFM ' FRONT SIDE OF TRACK ' 20 46 52 4F 4E 54 ...

String: " FRONT SIDE OF TRACK "

6EAAH

DEFB 03H 03

ETX terminator.

6EAB

DEFM 'FRONT' 46 52 4F 4E 54

String: "FRONT"

6EB0

DEFM ' BACK' 20 42 41 43 4B

String: " BACK"

6EB5H - Skip Whitespace and Check End

Utility routine to skip whitespace in command line input and check for end of line.

6EB5

CALL 6EC0H CD C0 6E

CALL 6EC0H - Check for end of line.

6EB8

RET Z C8

If Z FLAG (end of line), RETURN.

6EB9

CALL 4CD9H CD D9 4C

CALL 4CD9H (SYS0) - Skip whitespace.

6EBC

RET C D8

If Carry FLAG (found non-whitespace), RETURN.

6EBD

RET Z C8

If Z FLAG (end of line), RETURN.

6EBE

DEC HL 2B

Back up pointer.

6EBF

RET C9

RETURN.

6EC0H - Check End of Line

Checks if current character is end of line (0DH = carriage return).

6EC0

LD A,(HL) 7E

Load character at current position.

6EC1

CP 0DH FE 0D

Compare with 0DH (carriage return).

6EC3

RET Z C8

If Z FLAG (end of line), RETURN.

6EC4

CALL 4CD9H CD D9 4C

CALL 4CD9H (SYS0) - Check character type.

6EC7

RET NC D0

If NC FLAG (delimiter), RETURN.

6EC8