TRS-80 DOS – TRSDOS v1.3 – SYS09/SYS Disassembled – Ira Goldklang's TRS-80 Revived Site

General:

SYS09/SYS handles the COPY, DUAL, FORMS, KILL, MASTER, PATCH, RELO, ROUTE, SETCOM, and WP LIBrary Command.

Disassembly:

ORG 5200H

“BEGIN”
5200

LD A,55H

LET Register A = 55H (0101 0101).

5202

LD (42B4H),A

Store the value held in Register A into the memory location 42B4H.
NOTE: 42B4H is the storage location for the CLEAR RAM Flag.

5205

XOR A

Set Register A to ZERO and clear all Flags.

5206

LD (4414H),A

Clear the system flag by storing a 0 (held in Register A) into the memory location 4414H.
NOTE: 4414H is the storage location for the NUMBER OF THE OVERLAY CURRENTLY IN MEMORY.

5209

LD (42FFH),A

Clear the protection override flag by storing a 0 (held in Register A) into the memory location 42FFH.
NOTE: 42FFH is the storage location for whether a password check is skipped or undertaken in an OPEN command. If Bit 0 is set, the check is skipped.

520C

DEC A

DECrement the value stored in Register A by 1 so that Register A is now FFH.

520D

LD (427AH),A

Store the value held in Register A into the memory location 427AH. Putting a FFH (-1) here indicates that BASIC is not in RAM.

5210

PUSH HL

Save the POINTER TO THE COMMAND LINE in RAM (held in Register Pair HL) to the top of the stack.

5211

CALL GETTAB
[5226H]

Get the address of the command via a GOSUB to 5226H.

5214

JR C,NOCMD
[5218H]

If the C FLAG (Carry) has been set then the requested command is not one of the commands available in this overlay, so JUMP to 5218H.

5216

EX (SP),HL

EXchange the value stored in Register Pair HL (i.e., the POINTER TO THE COMMAND LINE in RAM) with the value stored at the top of the STACK (i.e., the command address).

5217

RET

RETurn to the caller.

5218H – Jumped to if the command requested is not one of the commands available in this overlay.

“NOCMD”
5218

POP HL

Put the value held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

“ERR”
5219

LD A,0BH

LET Register A = 0BH to indicate an illegal command parameter error.

521B

JR ERRX
[5223H]

Report the error and abort via a JUMP to 5223H.

521DH – Jumped here if we are missing the parameter.

“ERR3”
521D

LD A,0AH

LET Register A = 0AH to indicate a missing parameter.

521F

JR ERRX
[5223H]

Report the error and abort via a JUMP to 5223H.

5221H – Jumped here if we we were requested to do something to a drive which is not on the system.

“ERR9”
5221

LD A,02H

LET Register A = 02H to indicate the drive is not in the system.

“ERRX”
5223

JP 4409H
[4409H]

JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

5226H – Routine to do a Table Lookup.

“GETTAB”
5226

LD HL,TABLE

LET Register Pair HL = 523EH, which points to the lookup table.

“GETTA1”
5229

LD A,(HL)

Fetch the table compare byte (i.e., the value stored at the memory location pointed to by Register Pair HL) and put it into A.

522A

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

522B

JR NZ,522FH
[522FH]

If the NZ FLAG (Not Zero) has been set then we are not at the end of the table yet, so JUMP to 522FH to look it up.

522D

SCF

If we are here, then we ran out of table entries, so turn the CARRY FLAG on to indicate an error.

522E

RET

RETurn to the caller.

522FH – Continuation of the Table Lookup – Jumped here if the table compare byte matched.

“GETTA2”
522F

CP C

Compare the value held in Register A against the value held in Register C. Results: If Register A equals the value held in Register C, the Z FLAG is set; otherwise the NZ FLAG is set.

5230

JR Z,GETTA3
[5237H]

If the Z FLAG (Zero) has been set then we have a match! JUMP to 5237H to get the address.

5232
5233
5234

INC HL
INC HL
INC HL

If we’re here then we didn’t find a match, so we need to skip forward 3 bytes to the next entry.

5235

JR GETTA1
[5229H]

Loop back to 5229H to read the next table compare byte.

5237H – Continuation of the Table Lookup – Jumped here to load HL with the address of the matched routine.

“GETTA3”
5237

INC HL

INCrement the value stored in Register Pair HL by 1, so that HL now points to the LSB of the desired command.

5238

LD E,(HL)

Fetch the LSB of the desired command (i.e., stored at the memory location pointed to by Register Pair HL) and put it into E.

5239

INC HL

INCrement the value stored in Register Pair HL by 1, so that HL now points to the MSB of the desired command.

523A

LD D,(HL)

Fetch the MSB of the desired command (i.e., stored at the memory location pointed to by Register Pair HL) and put it into D.

523B

EX DE,HL

EXchange the value stored in Register Pair HL (i.e., the POINTER TO THE COMMAND LINE in RAM) with the value stored in Register Pair DE (i.e., the address of matching command).

523C

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

523D

RET

RETurn to the caller with the CARRY FLAG off so that we indicate NO ERROR.

523EH – Command Lookup Table.

“TABLE”
523E

DEFB 09H

09H = COPY command

523F

DEFB 5DH 52H

.. 525DH

5241

DEFB 0FH

0FH = DUAL command

5242

DEFB 34H 5FH

.. 5F34H

5244

DEFB 12H

12H = FORMS command

5245

DEFB 1FH 5BH

.. 5B1FH

5247

DEFB 16H

16H = KILL command

5248

DEFB 69H 56H

.. 5669H

524A

DEFB 1AH

1AH = MASTER command

524B

DEFB 3EH 60H

.. 603EH

524D

DEFB 1BH

1BH = PATCH command

524E

DEFB 1BH 57H

.. 571BH

5250

DEFB 1FH

1FH = RELO command

5251

DEFB 14H 5AH

.. 5A14H

5253

DEFB 21H

21H = ROUTE command

5254

DEFB 9AH 5BH

.. 5B9AH

5256

DEFB 22H

22H = SETCOM command

5257

DEFB 75H 5CH

.. 5C75H

5259

DEFB 25H

25H = WP command

525A

DEFB D9H 5FH

.. 5FD9H

525C

DEFB 00H

END OF TABLE MARKER

525DH – MAIN ROUTINE — COPY COMMAND

“COPY”
525D

PUSH HL

Save the POINTER TO THE COMMAND LINE in RAM (held in Register Pair HL) to the top of the stack.

525E

LD HL,54D0H

LET Register Pair HL = 54D0H to point to the COPY0 routine in this overlay as a vector. This will also be set by the KILL command and will point somewhere else.

5261

LD (5649H),HL

Store the value held in Register HL into the memory location 5649H, which is in the middle of a CALL OPCODE. This will set that OPCODE to “COPY”. The alternative would be from the “KILL” routine, which would set this to a different address.

5264

POP HL

Restore the POINTER TO THE COMMAND LINE in RAM held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

5265
5266

LD D,H
LD E,L

LET Register Pair DE = Register Pair HL (i.e., the first filespec).

5267

LD A,(DE)

Fetch the next character of the first filespec (stored at the memory location pointed to by Register Pair DE) and put it into A.

5268

CP 2FH

Compare the value held in Register A against /, which is a wildcard. Results: If Register A equals /, the Z FLAG is set; otherwise the NZ FLAG is set.

526A

JP Z,SLANT
[55B6H]

If the Z FLAG (Zero) has been set because we had a / then we know to copy everything; JUMP to 55B6H.

526D

CALL GETSYN
[59BCH]

OTHERWISE … GOSUB to 59BCH to process the first filespec (i.e., set Register Pair DE to point to the SOURCE FILE DCB, check the syntax of the associated Filespec, and RETurn).

5270

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

“”
5273

PUSH DE

Save the contents of Register Pair DE (the pointer to the first filespec on the command line) to the top of the stack.

5274

LD DE,6194H

Let Register Pair DE equal 6194H to point to the DESTINATION FILE DCB.

5277

CALL 441CH
[441CH]

GOSUB to 441CH to check the syntax of the second filespec.
NOTE: 441CH is the SYS00/SYS routine to CHECK THE SYNTAX OF A FILESPEC before for use. This RST 28H’s with a value of C1H so as to call ROUTINE 4 in OVERLAY 1.

527A

POP DE

Put the value held at the top of the STACK (the pointer to the first filespec on the command line) into Register Pair DE, and then remove the entry from the stack.

527B

JP Z,COPY9
[54A8H]

If the Z FLAG (Zero) has been set then we were given a good filespec, so JUMP to 54A8H.

527E

CP 3AH

Compare the value held in Register A against 3AH (ASCII: :) to see if we were only given a drive number. Results: If Register A equals :, the Z FLAG is set; otherwise the NZ FLAG is set.

5280

JR Z,CHECK
[528BH]

If the Z FLAG (Zero) has been set then we were only given a drive number, so JUMP to 528BH.

5282

CP 2EH

Compare the value held in Register A against 2EH (ASCII: .). Results: If Register A equals . then we were given a password, the Z FLAG is set; otherwise the NZ FLAG is set.

5284

JR Z,CHECK
[528BH]

If the Z FLAG (Zero) has been set, then we were given only a password and drive number, so JUMP to 528BH.

5286

CP 2FH

Compare the value held in Register A against 2FH (ASCII: /). Results: If Register A equals / then we were given only an extension, password, and filename and the Z FLAG is set; otherwise the NZ FLAG is set.

5288

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set then we weren’t given any of the above good parameters, so we have a problem, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

“CHECK”
528B

LD C,A

Copy the first character given for Filespec 2 (held in Register A) into Register C.

528C

LD B,00H

Set up Register B to be a counter by setting Register B to 00H.

528E

DEC HL

DECrement the value stored in Register Pair HL by 1 to point to the prior character.

“CHECK1”
528F

LD A,(DE)

Fetch the a character from Filespec 1 (held in the memory location pointed to by Register Pair DE) and store it into Register A.

5290

CP C

Compare the character from Filespec 2 (held in Register A) against the character from Filespec 1 (held in Register C). Results: If Register A equals the value held in Register C, the Z FLAG is set; otherwise the NZ FLAG is set.

5291

JR Z,CHECK2
[529BH]

If first characters from each filespec match, the Z FLAG (Zero) will have been set. JUMP to 529BH.

5293

CP 03H

Compare the value held in Register A against 03H (i.e., EOF) to check for the end of the filename. Results: If Register A equals 03H, the Z FLAG is set; otherwise the NZ FLAG is set.

5295

JR Z,CHECK2
[529BH]

If we reached the end of the filename, then the Z FLAG (Zero) will have been set. JUMP to 529BH.

5297

INC DE

Point Register Pair DE to the next character in Filespec 2 by bumping DE by 1.

5298

INC B

INCrement the counter stored in Register B by 1.

5299

JR CHECK1
[528FH]

LOOP BACK to 528FH to check the next character.

529BH – Part of the COPY routine; jumped here if the filename characters match.

“CHECK2”
529B

DEC HL

DECrement the pointer to the characters in Filespec 2 (stored in Register Pair HL) by 1.

529C

DEC DE

DECrement the pointer to the characters in Filespec 1 (stored in Register Pair DE) by 1.

529D

LD A,(DE)

Fetch a character from Filespec 1 (held in the memory location pointed to by Register Pair DE) and store it into Register A.

529E

LD (HL),A

Store the character from Filespec 1 into the corresponding characters lot of Filespec 2 (the memory location pointed to by Register Pair HL).

529F

DJNZ 529BH
[529BH]

LOOP back to 529BH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

52A1

JR 5273H
[5273H]

JUMP to 5273H to do another SYNTAX check.

52A3H – SUBROUTINE to bump the record number being processed and display that record number as being copied.

“DSPREC”
52A3

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

52A4

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

52A5

PUSH HL

Save the contents of Register Pair HL to the top of the stack.

52A6

LD HL,(RECCS)

Fetch the record number (held in memory location 52BAH) and store it into Register Pair HL.

52A9

INC HL

INCrement the record number (held in Register Pair HL) by 1.

52AA

LD (RECCS),HL

Store the bumped record number (held in Register Pair HL) into memory location 52BAH.

52AD

CALL ASCII
[52BCH]

GOSUB to 52BCH to convert the new record number to ASCII and put it into the message “COPYING RECORD nnnnn“.

52B0

LD HL,52DCH

Let Register Pair HL equal 52DCH, so as to point to the message “COPYING RECORD nnnn“.

52B3

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

52B6

POP HL

Put the value held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

52B7

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

52B8

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

52B9

RET

RETurn to the caller.

52BAH – MESSAGE and STORAGE AREA.

“RECCS”
52BA

DEFB xx xx

Storage Area for the Record Number of the Record Currently Being Copied.

52BCH – Subroutine to convert the new record number to ASCII and put it into the message “COPYING RECORD nnnn“..

“ASCII”
52BC

CALL 0A9AH
[0A9AH]

GOSUB to 0A9AH.
NOTE: 0A9AH is the Model III ROM routine to STORE AN INTEGER. The value in HL is put into the single precision number storage area of 4121H and is flagged as an INTEGER.

52BF

XOR A

Set Register A to ZERO and clear all Flags.

52C0

CALL 1034H
[1034H]

GOSUB to 1034H.
NOTE: 1034H is the Model III ROM routine to initialize the buffer for an ASCII conversion. It checks the edit flag (at 40D8H), sets HL to point to a buffer at 4130H, and puts a space there.

52C3

OR (HL)

Set the NZ Flag.

52C4

CALL 0FD9H
[0FD9H]

GOSUB to 0FD9H.
NOTE: 0FD9H is a routine which will convert the integer value in REG 1 (i.e., 4124H) to an ASCII string. Returns with register pair HL pointing to the result.

52C7

LD HL,4131H

Let Register Pair HL equal 4131H, to point to the ASCII converted number.

52CA

LD DE,RECNUM

Let Register Pair DE equal 52EDH, to point to the destination address in the message “COPYING RECORD nnnnn“.

52CD

LD B,05H

Let Register B equal 05H for a DJNZ loop of up to 5 characters.

“ASCII1”
52CF

LD A,(HL)

Fetch a converted character (held in the memory location pointed to by Register Pair HL) and store it into Register A.

52D0

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE). Results: If Register A equals SPACE, the Z FLAG is set; otherwise the NZ FLAG is set.

52D2

JR NZ,ASCII2
[52D6H]

If it’s not a space (and the NZ FLAG [Not Zero] has been set) then we don’t need to fill it with zeroes, so skip over the next instruction.

52D4

LD A,30H

Let Register A equal 30H (ASCII: 0).

“ASCII2”
52D6

LD (DE),A

Store the ASCII character held in Register A into the memory location pointed to by Register Pair DE.

52D7

INC HL

INCrement the value stored in Register Pair HL by 1 to point to the next number to convert.

52D8

INC DE

INCrement the value stored in Register Pair DE by 1 to point to the next location in the message “COPYING RECORD nnnnn“.

52D9

DJNZ ASCII1
[52CFH]

LOOP back to 52CFH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

52DB

RET

RETurn to the caller.

52DCH – MESSAGE and STORAGE AREA.

“RECORD”
52DC

DEFM →

“1DH + 1EH + ‘COPYING RECORD ‘“.

“RECNUM”

DEFM →

“‘nnnnn’ + 03H“.

52F3H – Subroutine to display the message COPYING filespec 1 TO filespec 2.

“DISPLY”
52F3

LD HL,COPMSG

Let Register Pair HL equal 531AH to point to the message “COPYING“.

52F6

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

52F9

LD HL,S9DCB1

Let Register Pair HL equal 6162H which is the beginning of the SOURCE FILE DCB. This would then point to the text of FILESPEC 1.

52FC

CALL PRNTIT
[5310H]

GOSUB to 5310H to display FILESPEC 1.

52FF

LD HL,TOO

Let Register Pair HL equal 5325H to point to the message “TO“.

5302

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

5305

LD HL,6194H

Let Register Pair DE equal 6194H to point to the DESTINATION FILE DCB, which starts with the filename.

5308

CALL PRNTIT
[5310H]

GOSUB to 5310H to display FILESPEC 2.

530B

LD A,0DH

Let Register A equal 0DH (ASCII: CARRIAGE RETURN).

530D

JP 0033H
[0033H]

JUMP to 0033H.
NOTE: 0033H is the Model III ROM character print routine; displays the character held in Register A at the current cursor position. Since this was JUMPED to instead of CALLed, the RET at the end of this ROM routine will then RETurn to the caller of this subroutine instead of returning to this place.

5310H – Subroutine of the Subroutine to display the message COPYING filespec 1 TO filespec 2. Parse the characters in the filespecs and display them.

“PRNTIT”
5310

LD A,(HL)

Fetch a charcter from the applicable filespec (held in the memory location pointed to by Register Pair HL) and store it into Register A.

5311

CP 21H

Compare the value held in Register A against / to see if we have reached the end of the filespec.

5313

RET C

If the character was a SPACE or lower, the C FLAG (Carry) has been set then we are at the end of the filespec so RETurn to the caller.

5314

CALL 0033H
[0033H]

GOSUB to 0033H.
NOTE: 0033H is the Model III ROM character print routine; displays the character held in Register A at the current cursor position.

5317

INC HL

Point to the next character in the filespec by bumping Register Pair HL by 1.

5318

JR PRNTIT
[5310H]

LOOP BACK to 5310H to keep displaying characters.

531AH – MESSAGE and STORAGE AREA.

“COPMSG”
531A

DEFM →

“
‘COPYING’ + 03H“.

“TOO”
5325

DEFM →

“
‘TO’ + 03H“.

532AH – Subroutine to display a flashing prompt of the message pointed to by Register Pair HL.

“S9WAIT”
532A

PUSH HL

Save the pointer to the message to be displayed (held in Register Pair HL) to the top of the stack.

532B

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

532E

POP HL

Restore the pointer to the message to be displayed (held at the top of the STACK) into Register Pair HL, and then remove the entry from the stack.

“LOOPY”
532F

LD BC,0256H

Let Register Pair BC equal 0256H to act as a timer.

“LOOPX”
5332

CALL 002BH
[002BH]

GOSUB to 002BH.
NOTE: 002BH is the Model III ROM Keyboard scanning routine; Register A exits with the ASCII value for the key that was pressed or ZERO if no key was pressed.

5335

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN, the Z FLAG is set; otherwise the NZ FLAG is set.

5337

JR Z,LINOFF
[534DH]

If we got a CARRIAGE RETURN from the user, the Z FLAG (Zero) will have been set; JUMP to 534DH.

“”
5339

DEC BC

DECrement the counter (stored in Register Pair BC) by 1.

533A
533A

LD A,B
OR C

Since the Z-80 cannot test Register Pair BC against zero, the common trick is to set Register A to equal to Register B, and then OR A against Register C. Only if both Register B and Register C were zero can the Z FLAG be set.

533C

JR NZ,LOOPX
[5332H]

If the NZ FLAG (Not Zero) has been set, then we still have more counting to do, so LOOP BACK to 5332H.

533E

LD A,(FSFLAG)

Fetch the value of the flag held in memory location 54A7H and store it into Register A.

5341

XOR 01H

Toggle the flag.

5343

LD (FSFLAG),A

Store the toggled flag (held in Register A) back into memory location 54A7H.

5346

JR Z,SWAIT
[532AH]

If the toggled flag hit 0, the Z FLAG (Zero) will have been set, JUMP to 532AH to redisplay.

5348

CALL LINOFF
[534DH]

Otherwise we want to blank the line so it flashes via a GOSUB to 534DH.

534B

JR LOOPY
[532FH]

Loop back to to 532FH.

534DH – Jump point in the subroutine to display a flashing prompt of the message pointed to by Register Pair HL. Jumped here if we got a CARRIAGE RETURN from the user.

“LINOFF”
534D

LD A,1DH

Let Register A equal 1DH (ASCII: Move cursor to start of line).

534F

CALL 0033H
[0033H]

GOSUB to 0033H.
NOTE: 0033H is the Model III ROM character print routine; displays the character held in Register A at the current cursor position.

5352

LD A,1EH

Let Register A equal 1EH (ASCII: Clear to end of line).

5354

JP 0033H
[0033H]

5357H – Single Drive, Single File Copy Routine.

This routine finds out how much user ram is available, and reads the first file until EOF or memory full. Ask to swap disks and write until the file is written; swapping back if memory ran out before EOF.

“”
5357

LD HL,(4415H)

Fetch the address of the end of usable memory (held in memory location 4415H) and store it into Register Pair HL.

535A

LD DE,BUFER1

Let Register Pair DE equal 6300H to point to the READ FILE buffer.

535D

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

535E

SBC HL,DE

Determine the number of bytes left in RAM by subtracting the top of the buffer (6300H, stored in Register Pair DE) and the carry flag from the end of usable RAM (stored in Register Pair HL).

5360

LD DE,0100H

Let Register Pair DE equal 0100H (Decimal: 256), which is the size of 1 sector, to prepare for a division.

5363

LD B,00H

Let Register B equal 00H as B will be a counter of the number of blocks of available free RAM.

“LOOPZ”
5365

INC B

INCrement the block counter (stored in Register B) by 1.

5366

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5367

SBC HL,DE

Do division by subtraction by subtracting (with carry) 256 (held in Register Pair DE) from the number of bytes of free RAM (held in Register Pair HL).

5369

JR NC,LOOPZ
[5365H]

If that subtraction didn’t wind up going negative (so NC is set), then we can continue to divide, so JUMP to 5365H.

536B

LD A,B

Copy the number of blocks of free RAM (held in Register B) into Register A.

536C

DEC A

Round down by 1 block via a DECrement of Register A.

536D

LD (FLFAG),A

Store the number blocks of free RAM (held in Register A) into memory location 54A6H.

5370

LD HL,S9SRC

Let Register Pair HL equal 5487H, which is a pointer to the “1DH + “
‘Insert SOURCE Disk (ENTER) ‘ + 03H”

5373

CALL S9WAIT
[532AH]

GOSUB to 532AH, which is the flashing prompt routine.

5376

CALL OPENIT
[599BH]

We got the user response, so GOSUB to 599BH to open the source file.

5379

LD IX,S9DCB1

Let Special Index Register Pair IX equal 6162H which is the beginning of the SOURCE FILE DCB.

537D

RES 7,(IX+01H)

RESet (i.e., set as 0) BIT 7 of the value stored at the memory location pointed to by Register IX+01H so that the the LRL will be 256.

5381

LD A,(IX+09H)

Fetch the LRL (held in the memory location pointed to by Special Index Register Pair IX+09H) and store it into Register A.
Note: IX+09H = the position in the DCB for the LOGICAL RECORD LENGTH).

5384

LD (ADD1),A

Store the LRL (held in Register A) into memory location 56D5H.

5387

LD A,(IX+08H)

Fetch the byte of the EOF (held in the memory location pointed to by Special Index Register Pair IX+08H) and store it into Register A.
Note: IX+08H = the position in the DCB for the BYTE OFFSET IN THE SECTOR FOR LAST BYTE OF THE FILE).

538A

LD (56D6H),A

Store the byte of the EOF (held in Register A) into memory location 56D6H.

538D

XOR A

Set Register A to ZERO and clear all Flags, which also prepares to desginate a LRL of 256 (which is a force for FULL SECTOR I/O).

538E

LD (LRLCHG),A

Store the value held in Register A (i.e., a 0) into memory location 53A4H which is in the middle of a LD B,xx OPCODE.

5391

LD A,(IX+0CH)

Fetch the value held in the memory location pointed to by Special Index Register Pair IX+0CH and store it into Register A.
Note: IX+0CH = the position in the DCB for the NMSB OF THE LAST SECTOR TO READ/EOF)

5394

LD (56D7H),A

Store the value held in Register A into memory location 56D7H.

5397

LD A,(IX+0DH)

Fetch the value held in the memory location pointed to by Special Index Register Pair IX+0DH and store it into Register A.
Note: IX+0DH = the position in the DCB for the MSB OF THE LAST SECTOR TO READ/EOF)

539A

LD (56D8H),A

Store the value held in Register A into memory location 56D8H.

539D

LD HL,S9DES

Let Register Pair HL equal 5463H, which is a pointer to the “1DH + ‘Insert DESTINATION Disk (ENTER) ‘ + 03H” Message.

53A0

CALL S9WAIT
[532AH]

GOSUB to 532AH, which is the flashing prompt routine.

53A3

LD B,LRLCHG

Let Register B equal the LRL placed here at 538EH.

53A5

LD DE,6194H

Let Register Pair DE equal 6194H to point to the DESTINATION FILE DCB.

53A8

LD HL,BUFER1

Let Register Pair HL equal 6300H to point to the beginning of the READ FILE buffer.

53AB

CALL 4420H
[4420H]

GOSUB to 4420H.
NOTE: 4420H is the SYS00/SYS routine to INITIALIZE A FILE (i.e., CREATE or OPEN). This RST 28H’s with a value of A2H so as to call ROUTINE 2 in OVERLAY 2. Register HL needs to point to a RAM BUFFER for the DCB’s.

53AE

JP NZ,ERRX
[5223H]

If the NZ FLAG (Not Zero) has been set, then that CALL returned an error; report the error and abort via a JUMP to 5223H.

“LOOPZ0”
53B1

LD HL,S9SRC

Let Register Pair HL equal 5487H, which is a pointer to the “1DH + “
‘Insert SOURCE Disk (ENTER) ‘ + 03H”

53B4

CALL S9WAIT
[532AH]

GOSUB to 532AH, which is the flashing prompt routine.

53B7

LD HL,BUFER1

Let Register Pair HL equal 6300H to point to the beginning of the READ FILE buffer.

53BA

LD (6165H),HL

Store the pointer to the READ FILE BUFFER (held in Register Pair HL) into memory location 6165H, which is the DCB Buffer Address Location.

53BD

LD A,(FLFLAG)

Fetch the number of blocks of RAM (held in memory location 54A6H) and store it into Register A.

53C0

LD B,A

Copy the contents of Register A into Register B so that Register B can act as a DJNZ counter of blocks to read into RAM.

“LOOPZ1”
53C1

PUSH BC

Save the counter (held in Register Pair BC) to the top of the stack.

53C2

LD DE,S9DCB1

Let Register Pair DE equal 6162H which is the beginning of the SOURCE FILE DCB.

53C5

CALL 4436H
[4436H]

Read 1 block via a GOSUB to 4436H.
NOTE: 4436H is the SYS00/SYS vector for ‘READ’, which reads the record that the disk drive is positioned over.

53C8

POP BC

Restore the counter from the top of the STACK into Register Pair BC, and then remove the entry from the stack.

53C9

JR Z,LOOPZ2
[53D6H]

If the Z FLAG (Zero) has been set then there is no error, so JUMP to 53D6H.

53CB

CP 1CH

Compare the value held in Register A against 1CH (i.e., EOF ERROR). Results: If Register A equals 1CH, the Z FLAG is set; otherwise the NZ FLAG is set.

53CD

JR Z,GOGO
[540EH]

If we have an EOF ERROR, then the Z FLAG (Zero) will have been set, BUT, we are done with the read anyway, so JUMP to 540EH.

53CF

CP 1DH

Compare the value held in Register A against 1DH (i.e., RECORD OUT OF RANGE ERROR). Results: If Register A equals 1DH, the Z FLAG is set; otherwise the NZ FLAG is set.

53D1

JR Z,GOGO
[540EH]

If we have an RECORD OUT OF RANGE ERROR, then the Z FLAG (Zero) will have been set, BUT, we are done with the read anyway, so JUMP to 540EH.

53D3

JP ERRX
[5223H]

If we’re here, then we have another error that we do care about; report the error and abort via a JUMP to 5223H.

53D6H – Continuation of SINGLE FILE, SINGLE DRIVE Copy – Jumped here when a block as successfully been read into the READ FILE BUFFER.

“LOOPZ2”
53D6

LD HL,(6165H)

Fetch the pointer to DCB Buffer Address in the READ FILE BUFFER (held at 6165H) into Register Pair HL.

53D9

LD DE,0100H

Let Register Pair DE equal 0100H (Decimal: 256), which is 1 block.

53DC

ADD HL,DE

Move to the next block of RAM in the READ BUFFER by bumping the READ BUFFER forward 256 bytes (1 block).

53DD

LD (6165H),HL

Store the newly bumped pointer to DCB Buffer Address in the the READ FILE BUFFER (held in Register Pair HL) into memory location 6165H, which is the DCB Buffer Address Location.

53E0

DJNZ LOOPZ1
[53C1H]

LOOP back to 53C1H to keep reading until the buffer is full, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

At this point, the READ RAM buffer has been filled, so now we need to write it to disk.

53E2

LD HL,S9DES

Let Register Pair HL equal 5463H, which is a pointer to the “1DH + ‘Insert DESTINATION Disk (ENTER) ‘ + 03H” Message.

53E5

CALL S9WAIT
[532AH]

GOSUB to 532AH, which is the flashing prompt routine.

53E8

LD HL,BUFER1

Let Register Pair HL equal 6300H to point to the beginning of the READ FILE buffer.

53EB

LD (6165H),HL

Store the READ FILE buffer into the address for the read DCB buffer pointer, resetting it.

53EE

LD (6197H),HL

Store the DCB Buffer Address (held in Register Pair HL) into the DCB Buffer Address for the DESTINATION FILE BUFFER (held in 6197H).

53F1

LD A,(FLFLAG)

Fetch the buffer size in blocks (held in memory location 54A6H) and store it into Register A.

53F4

LD B,A

Copy the contents of Register A into Register B so that Register B can act as a DJNZ counter of blocks to read into RAM.

“LOOPZ3”
53F5

PUSH BC

Save the block counter (held in Register Pair BC) to the top of the stack.

53F6

LD DE,6194H

Let Register Pair DE equal 6194H to point to the DESTINATION FILE DCB.

53F9

CALL 443CH
[443CH]

Write with Verify via a CALL to 443CH
NOTE: 443CH is the SYS00/SYS vector for ‘WRITE with VERIFY’, which will write verify a write with a retry count of 3. DE must point to the buffer to write.

53FC

POP BC

Restore the block counter (held at the top of the STACK) into Register Pair BC, and then remove the entry from the stack.

53FD

JP NZ,ERRX
[5223H]

If the NZ FLAG (Not Zero) has been set, then that CALL returned an error; report the error and abort via a JUMP to 5223H.

5400

LD HL,(6197H)

Fetch the DCB Buffer Address in the DESTINATION FILE BUFFER (held in memory location 6197H) and store it into Register Pair HL.

5403

LD DE,0100H

Let Register Pair DE equal 0100H (Decimal: 256), which is 1 block.

5406

ADD HL,DE

Bump the DCB Buffer Address in the the DESTINATION FILE BUFFER by 256 (which is 1 block) to point to the next block to write.

5407

LD (6197H),HL

Store the bumped DCB Buffer Address (held in Register Pair HL) into the DCB Buffer Address for the DESTINATION FILE BUFFER (held in 6197H).

540A

DJNZ LOOPZ3
[53F5H]

LOOP back to 53F5H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

540C

JR LOOPZ0
[53B1H]

JUMP to 53B1H to move to the next read.

540EH – Continuation of SINGLE FILE, SINGLE DRIVE Copy – Jumped here to write out what we have if we had a (harmless) EOF error or Records Out of Range error.

“GOGO”
540E

LD A,(FLFLAG)

Fetch the size of the RAM buffer (in blocks) (held in memory location 54A6H) and store it into Register A.

5411

SUB B

LET Register A = the size of the RAM buffer (held in Register A) – the number of blocks we have actually read so far (held in Register B).

5412

LD B,A

Copy the contents of Register A into Register B so that B can act as a counter.

5413

PUSH BC

Save the block counter (held in Register Pair BC) to the top of the stack.

5414

LD HL,S9DES

Let Register Pair HL equal 5463H, which is a pointer to the “1DH + ‘Insert DESTINATION Disk (ENTER) ‘ + 03H” Message.

5417

CALL S9WAIT
[532AH]

GOSUB to 532AH, which is the flashing prompt routine.

541A

LD HL,BUFER1

Let Register Pair HL equal 6300H to point to the beginning of the READ FILE buffer.

541D

LD (6197H),HL

Store the DCB Buffer Address (held in Register Pair HL) into the DCB Buffer Address for the DESTINATION FILE BUFFER (held in 6197H).

5420

POP BC

Restore the block counter (held at the top of the STACK) into Register Pair BC.

“GOGO1”
5421

PUSH BC

Save the block counter (held in Register Pair BC) to the top of the stack.

5422

LD DE,6194H

Let Register Pair DE equal 6194H to point to the DESTINATION FILE DCB (of 6194H).

5425

CALL 443CH
[443CH]

5428

POP BC

Restore the block counter (held at the top of the STACK) into Register Pair BC.

5429

JP NZ,ERRX
[5223H]

If the NZ FLAG (Not Zero) has been set, then that CALL returned an error; report the error and abort via a JUMP to 5223H.

542C

LD HL,(6197H)

Fetch the DCB Buffer Address in the DESTINATION FILE BUFFER (held in memory location 6197H) and store it into Register Pair HL.

542F

LD DE,0100H

Let Register Pair DE equal 0100H (Decimal: 256), which is 1 block.

5432

ADD HL,DE

Bump the DCB Buffer Address in the the DESTINATION FILE BUFFER by 256 (which is 1 block) to point to the next block of RAM to write.

5433

LD (6197H),HL

Store the bumped DCB Buffer Address (held in Register Pair HL) into the DCB Buffer Address for the DESTINATION FILE BUFFER (held in 6197H).

5436

DJNZ GOGO1
[5421H]

LOOP back to 5421H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

At this point, the buffers have been written, but the EOF cannot simply be transferred because of the EOF / RECORD OUT OF RANGE error on the read, so we need to recalculate and set the appropriate EOF.

5438

LD IX,6194H

Let Special Index Register IX equal 6194H to point to the DESTINATION FILE DCB (of 6194H).

543C

LD A,(ADD1)

Fetch the LRL (held in memory location 56D5H) and store it into Register A.

543F

LD (IX+09H),A

Store the value held in Register A into the memory location pointed to by Special Index Register Pair IX+09H.
Note: IX+09H = the position in the DCB for the LOGICAL RECORD LENGTH).

5442

LD A,(56D6H)

Fetch the byte of EOF (held in memory location 56D6H) and store it into Register A.

5445

LD (IX+08H),A

Store the value held in Register A into the memory location pointed to by Special Index Register Pair IX+08H.
Note: IX+08H = the position in the DCB for the BYTE OFFSET IN THE SECTOR FOR LAST BYTE OF THE FILE).

5448

LD A,(56D7H)

Fetch the LSB of the SECTOR EOF (held in memory location 56D7H) and store it into Register A.

544B

LD (IX+0CH),A

Store the value held in Register A into the memory location pointed to by Special Index Register Pair IX+0CH.
Note: IX+0CH = the position in the DCB for the NMSB OF THE LAST SECTOR TO READ/EOF)

544E

LD A,(56D8H)

Fetch the MSB of the SECTOR EOF (held in memory location 56D8H) and store it into Register A.

5451

LD (IX+0DH),A

Store the value held in Register A into the memory location pointed to by Special Index Register Pair IX+0DH.
Note: IX+0DH = the position in the DCB for the MSB OF THE LAST SECTOR TO READ/EOF)

5454

LD DE,6194H

Let Register Pair DE equal 6194H to point to the DESTINATION FILE DCB (of 6194H).

5457

CALL 4428H
[4428H]

GOSUB to 4428H to CLOSE the file
NOTE: 4428H is the SYS00/SYS routine to CLOSE A DISK FILE. This RST 28H’s with a value of 93H so as to call ROUTINE 1 in OVERLAY 3.

545A

LD HL,S9SRC

Let Register Pair HL equal 5487H, which is a pointer to the “1DH + “
‘Insert SOURCE Disk (ENTER) ‘ + 03H”

545D

CALL S9WAIT
[532AH]

GOSUB to 532AH, which is the flashing prompt routine.

5460

JP CCLSE1
[5551H]

JUMP to 5551H to close the file and exit.

5463H – MESSAGE and STORAGE AREA.

“DEF9DES”
5463

DEFM →

“1DH + ‘Insert DESTINATION Disk (ENTER) ‘ + 03H” Message.

“DEF9SRC”
5487

DEFM →

“1DH + “
‘Insert SOURCE Disk (ENTER) ‘ + 03H”.

“FLFLAG”
54A6

DEFB 00H

Number of blocks available in RAM to use for the copy.

“FSFLAG”
54A7

DEFB 00H

Toggle for the flash in the flashing message.

54B9H – SINGLE DRIVE COPY ROUTINE – See if the user has selected the drives to make this a single drive copy. This portion parses both for a drive number, and defaults to “0” if none.

“COPY9”
54A8

LD HL,S9DCB1

Let Register Pair HL equal 6162H which is the beginning of the SOURCE FILE DCB, and, in specific, the filespec (which appears at the beginning of the DCB).

54AB

LD B,18H

Let Register B equal 18H (Decimal: 24) for a count of 24, which is (1 more than) the number of characters in filename/ext.password:d.

“COP90”
54AD

LD A,(HL)

Fetch a character from filespec in the SOURCE FILE DCB (the memory location pointed to by Register Pair HL) and store it into Register A.

54AE

CP 3AH

Compare the value held in Register A against 3AH (ASCII: :) to test for a drivespec.

“”
54B0

INC HL

INCrement the pointer to the SOURCE FILE DCB (held in Register HL) by 1 to point to the next character.

54B1

JR Z,COP91
[54B9H]

If we got a “:” then the Z FLAG (Zero) would have been set, so JUMP to 54B9H to test the drive.

54B3

DJNZ COP90
[54ADH]

Parse the entire filespec portion of the SOURCE FILE DCB by LOOPing back to 54ADH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

54B5

LD C,30H

Let Register C equal 30H (ASCII: 0) as a default drive.

54B7

JR COP910
[54BAH]

JUMP to 54BAH to process the SOURCE FILE with a drive of “0” (i.e., skip the next instruction which sets Register C to something else).

54B9H – Continuation of the routine to see if the user has selected the drives to make this a single drive copy; jumped here if a we got a “:” in the SOURCE FILE DCB.

“COP91”
54B9

LD C,(HL)

Fetch a character from filespec held in the SOURCE FILE DCB (the memory location pointed to by Register Pair HL), which is hopefuly a drive number since it follows a “:”, into Register C.

“COP910”
54BA

LD HL,6194H

Let Register Pair HL equal 6194H to point to the DESTINATION FILE DCB, which will also point to the filespec in the DESTINATION FILE DCB.

54BD

LD B,18H

Let Register B equal 18H (Decimal: 24) for a count of 24, which is (1 more than) the number of characters in filename/ext.password:d.

“COP92”
54BF

LD A,(HL)

Fetch a character from the filespec of the DESTINATION FILE DCB (the memory location pointed to by Register Pair HL) and store it into Register A.

54C0

CP 3AH

Compare the value held in Register A against 3AH (ASCII: :) to test for a drivespec.

54C2

INC HL

INCrement the pointer to the DESTINATION FILE DCB (held in Register HL) 1 to the next character.

54C3

JR Z,COP93
[54CBH]

If we got a “:” then the Z FLAG (Zero) would have been set, so JUMP to 54B9H to test the drive.

54C5

DJNZ COP92
[54BFH]

Parse the entire filespec portion of the DESTINATION FILE DCB by LOOPing back to 54BFH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

54C7

LD A,30H

Let Register A equal 30H (ASCII: 0) as a default drive.

54C9

JR COP930
[54CCH]

JUMP to 54CCH to process the DESTINATION FILE with a drive of “0” (i.e., skip the next instruction which sets Register C to something else).

54CBH – Continuation of the routine to see if the user has selected the drives to make this a single drive copy; check the two drive numbers (held in A and C) to see if they match.

“COP93”
54CB

LD A,(HL)

Fetch a the drive number from the DESTINATION FILE DCB (the memory location pointed to by Register Pair HL) and store it into Register A.

“COP930”
54CC

CP C

Compare the drive number from the DESTINATION FILE DCB (held in Register a) against the drive number from the READ FILE DCB (held in Register C). Results: If Register A equals the value held in Register C, the Z FLAG is set; otherwise the NZ FLAG is set.

54CD

JP Z,SINGCP
[5357H]

If they match, then the Z FLAG (Zero) will have been set; JUMP to 5357H to do a single drive copy.

54D0H – Dual Drive copy roputine.

“COPY0”
54D0

CALL DISPLY
[52F3H]

GOSUB to 52F3H to display the message COPYING filespec 1 TO filespec 2.

54D3

LD HL,0FFFFH

Let Register Pair HL equal 0FFFFH (i.e., -1) to act as a counter.

54D6

LD (RECCS),HL

Store the value held in Register Pair HL into memory location 52BAH, which tracks the RECORD NUMBER BEING COPIED.

54D9

CALL OPENIT
[599BH]

OPEN the file via a GOSUB to 599BH.

54DC

JP NZ,ERRX
[5223H]

If the NZ FLAG (Not Zero) has been set, then that CALL returned an error; report the error and abort via a JUMP to 5223H.

54DF

LD B,LRLCH1

Let Register B equal the value put into 54E0H elsewhere, which, if 0, is a LRL of 256.

54E1

LD DE,6194H

Let Register Pair DE equal 6194H to point to the DESTINATION FILE DCB.

54E4

LD HL,6400H

Let Register Pair HL equal 6400H to point to the beginning of the DESTINATION FILE buffer.

54E7

CALL 4420H
[4420H]

Create the destination file via a GOSUB to 4420H.
NOTE: 4420H is the SYS00/SYS routine to INITIALIZE A FILE (i.e., CREATE or OPEN). This RST 28H’s with a value of A2H so as to call ROUTINE 2 in OVERLAY 2. Register HL needs to point to a RAM BUFFER for the DCB’s.

54EA

JP NZ,ERRX
[5223H]

If the NZ FLAG (Not Zero) has been set, then that CALL returned an error; report the error and abort via a JUMP to 5223H.

“CONTT”
54ED

CALL DSPREC
[52A3H]

Display the record number via a GOSUB to 52A3H.

54F0

LD DE,S9DCB1

Let Register Pair DE equal equal 6162H which is the beginning of the SOURCE FILE DCB.

54F3

LD HL,6200H

Let Register Pair HL equal 6200H to point to the SOURCE FILE DCB at 6200H (which is used for non 256 LRL files).

54F6

CALL 4436H
[4436H]

Read a record from the SOUCE FILE into the buffer pointed to by Register Pair HL via a GOSUB to 4436H.
NOTE: 4436H is the SYS00/SYS vector for ‘READ’, which reads the record that the disk drive is positioned over.

54F9

JR Z,NEXT
[5506H]

If the Z FLAG (Zero) has been set then there was no error, so do the WRITE via a JUMP to 5506H.

54FB

CP 1CH

Compare the value held in Register A against 1CH (i.e., EOF ERROR). Results: If Register A equals 1CH, the Z FLAG is set; otherwise the NZ FLAG is set.

54FD

JR Z,DONE0
[5525H]

If the Z FLAG (Zero) has been set we have an EOF error, but we are also done; so JUMP to 5525H.

54FF

CP 1DH

Compare the value held in Register A against 1DH (i.e., RECORD OUT OF RANGE ERROR). Results: If Register A equals 1DH, the Z FLAG is set; otherwise the NZ FLAG is set.

5501

JR Z,DONE0
[5525H]

If the Z FLAG (Zero) has been set we have a RECORD OUT OF RANGE error, but we are also done, so JUMP to 5525H.

5503

JP ERRX
[5223H]

If we’re here then we have an error we care about, so report the error and abort via a JUMP to 5223H.

5506H – Copy the READ FILE BUFFER to the DESTINATION FILE BUFFER, and WRITE.

“NEXT”
5506

LD A,(616BH)

Fetch the LRL of the SOURCE FILE (held in memory location 616BH) and store it into Register A.

5509

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

550A

JR NZ,NEXTV
[5517H]

If the NZ FLAG (Not Zero) has been set, then we do not have a LRL of 256, so JUMP to 5517H.

550C

LD HL,BUFER1

Let Register Pair HL equal 6300H to point to the beginning of the READ FILE buffer.

550F

LD DE,6400H

Let Register Pair DE equal 6400H to point to the beginning of the DESTINATION FILE buffer.

5512

LD BC,0100H

Let Register Pair DE equal 0100H (Decimal: 256) to prepare for a LDIR move of 256 bytes.

5515

LDIR

Transfers a byte of data from the memory location pointed to by HL to the memory location pointed to by DE. Then HL and DE are incremented and BC is decremented. If BC is not zero, this operation is repeated. Interrupts can trigger while this instruction is processing.

“NEXTV”
5517

LD DE,6194H

Let Register Pair DE equal 6194H to point to the DESTINATION FILE DCB.

551A

LD HL,6200H

Let Register Pair HL equal 6200H to point to buffer number 4 (which is used for non 256 LRL files).

551D

CALL 4439H
[4439H]

Write out the record via a GOSUB to 4439H.

5520

JR Z,54EDH
[54EDH]

If the Z FLAG (Zero) has been set then the write was successful, so do move via a LOOP BACK to 54EDH.

5522

JP ERRX
[5223H]

Report the error and abort via a JUMP to 5223H.

5525H – The copy routine has completed but with a (harmless) EOF or RECORD OUT OF RANGE ERROR.

“DONE0”
5525

LD A,(616BH)

Fetch the LRL of the SOURCE FILE (held in memory location 616BH) and store it into Register A.

5528

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5529

JR NZ,DONE1
[5542H]

If the NZ FLAG (Not Zero) has been set, then the LRL is not a standard 256 (i.e., we do not have a full sector), so JUMP to 5542H to deal with that.

552B

LD A,(616AH)

Fetch the EOF BYTE of the SOURCE FILE (held in memory location 616AH) and store it into Register A.

552E

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

552F

JR Z,5542H
[5542H]

If the Z FLAG (Zero) has been set, then the EOF is on the sector boundary and we don’t need to do any special math to calculate it, so continue via a JUMP to 5542H.

If we are here then we need to specially calculate the EOF.

5531

LD IX,6194H

Let Special Index Register IX equal 6194H to point to the DESTINATION FILE DCB.

5535

LD L,(IX+0CH)

Fetch the value held in the memory location pointed to by Special Index Register Pair IX+0CH and store it into Register L.
Note: IX+0CH = the position in the DCB for the LSB OF THE LAST SECTOR TO READ/EOF)

5538

LD H,(IX+0DH)

Fetch the value held in the memory location pointed to by Special Index Register Pair IX+0DH and store it into Register H.
Note: IX+0DH = the position in the DCB for the MSB OF THE LAST SECTOR TO READ/EOF)

553B

DEC HL

DECrement the value stored in Register Pair HL by 1 to back up the EOF one record.

553C

LD (IX+0CH),L

Store the adjusted EOF byte held in Register L into the memory location pointed to by Special Index Register Pair IX+0CH.
Note: IX+0CH = the position in the DCB for the NMSB OF THE LAST SECTOR TO READ/EOF)

553F

LD (IX+0DH),H

Store the adjusted EOF byte held in Register H into the memory location pointed to by Special Index Register Pair IX+0DH.
Note: IX+0DH = the position in the DCB for the MSB OF THE LAST SECTOR TO READ/EOF)

“DONE1”
5542

LD A,(616AH)

Fetch the EOF BYTE of the SOURCE FILE (held in memory location 616AH) and store it into Register A.

5545

LD (619CH),A

Store the the EOF BYTE of the SOURCE FILE (held in Register A) into the DESTINATION FILE DCB (held at memory location 619CH).

“CCLSE”
5548

LD DE,6194H

Let Register Pair DE equal 6194H to point to the DESTINATION FILE DCB.

554B

CALL 4428H
[4428H]

GOSUB to 4428H to CLOSE the file
NOTE: 4428H is the SYS00/SYS routine to CLOSE A DISK FILE. This RST 28H’s with a value of 93H so as to call ROUTINE 1 in OVERLAY 3.

554E

JP NZ,ERRX
[5223H]

If the NZ FLAG (Not Zero) has been set, then that CALL returned an error; report the error and abort via a JUMP to 5223H.

“CCLSE1”
5551

LD DE,S9DCB1

Let Register Pair DE equal equal 6162H which is the beginning of the SOURCE FILE DCB.

“CCLSE2”
5554

CALL 4428H
[4428H]

GOSUB to 4428H to CLOSE the file
NOTE: 4428H is the SYS00/SYS routine to CLOSE A DISK FILE. This RST 28H’s with a value of 93H so as to call ROUTINE 1 in OVERLAY 3.

5557

JP NZ,ERRX
[5223H]

If the NZ FLAG (Not Zero) has been set, then that CALL returned an error; report the error and abort via a JUMP to 5223H.

555A

RET

RETurn to the caller.

555BH – MESSAGE and STORAGE AREA.

“DRIVE1”
531A

DEFM “:0” + 0DH

Storage for the SOURCE DRIVESPEC.

“DRIVE2”
555E

DEFM “:1” + 0DH

Storage for the DESTINATION DRIVESPEC.

“ZSLANT”
5561

DEFM “/”

Storage for an extension (part 1). This would also be thhe wild-card extension.

“S9CMD”
5562

DEFM “BAS”

Storage for an extension (part 2).

“SAVE3”
5565

DEFW 00H 43H

Buffer Starting Address

“S9TRK”
5567

DEFB 00H

Storage for the current/desired sector number in the directory sector.

5568H – Read the Directory Track into a Buffer at 4300H.

“GETDIR”
5568

LD A,(DRIVE1 + 1)

Fetch the drive number (held in memory location 555CH) and store it into Register A.

556B

AND 0FH

MASK the value of Register A against 0FH (0000 1111) to leave only bits 3, 2, 1, 0 active; basically turning the ASCII into BINARY.

556D

LD C,A

Copy binary rendition of the drive number (held in Register A) into Register C.

556E

CALL 4B3EH
[4B3EH]

Get the directory track via a GOSUB to 4B3EH.
NOTE: 4B3EH is the SYS00/SYS routine to identify the track number of the directory. Routine exits with the director track number in Register D.

5571

LD A,(S9TRK)

Fetch the directory sector we want to read (held in memory location 5567H) and store it into Register A.

5574

LD E,A

Copy the the directory sector we want to read (held in Register A) into Register E.

5575

LD HL,4300H

Let Register Pair HL equal 4300H, whiich will be a buffer.

5578

CALL 4675H
[4675H]

GOSUB to 4675H of SYS00/SYS to position the drive head and read the requested sector into the buffer pointed to by Register Pair HL.

557B

RET

RETurn to the caller.

557CH – Routine to transfer B number of characters from (DE) to (IX), aborting if a SPACE is found.

“MOVE1”
557C

LD A,(DE)

Fetch a character held in the memory location pointed to by Register Pair DE and store it into Register A.

557D

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE).

557F

POP IY

In case there is a match, and we therefore have an illegal character, and we need to clear the return address from the top of the STACK.

5581

JP Z,ERR2
[5219H]

If we got a SPACE, which is bad, the Z FLAG (Zero) will have been set, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5584

PUSH IY

If we are here, then we didn’t get an illegal character, so put the return address back to the top of the stack.

5586

LD (IX),A

Store the character we read (held in Register A) into the memory location pointed to by Special Index Register Pair IX+00H.
Note: IX+00H = the position in the DCB for the TYPE of FCB byte. Bit 0: 1=Read Only, Bit 1: 1=Write Only, Bit 4: 1=The next 2 bytes are simply the address of another FCB, Bit 7=1: Then the next 50 bytes are the description of an open file.

5589

INC DE

INCrement the value stored in Register Pair DE by 1 to point to the next character to test.

558A

INC IX

INCrement the value stored in Special Index Register IX by 1 to move to the next area to save the character to.

558C

DJNZ MOVE1
[557CH]

LOOP back to 557CH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

558E

RET

RETurn to the caller.

558FH – Routine to copy a filename from the directory entry (pointed to by DE) into the DCB (pointed to HL); returns with Register C containing the number of characters in the filename.

“MOVE2”
558F

LD B,08H

Let Register B equal 08H as there are 8 characters in a filespec.

“MOVE20”
5591

LD A,(DE)

Fetch a character (held in the memory location pointed to by Register Pair DE) and store it into Register A.

5592

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE).

5594

RET Z

If we got a SPACE then we are done; so RETURN.

5595

LD (HL),A

If we are here, the character is good, so store the character (held in Register A) into the DCB (pointed to by Register Pair HL).

5596

INC C

INCrement the counter (Register C) by 1.

5597

INC HL

INCrement the pointer for the destination (stored in Register Pair HL) by 1.

5598

INC DE

INCrement the pointer for the source (stored in Register Pair DE) by 1.

5599

DJNZ MOVE20
[5591H]

LOOP back to 5591H for up to 8 iterations, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

559B

RET

RETurn to the caller.

559CH – Routine to copy an extension from the directory entry (pointed to by DE) into the DCB (pointed to HL); returns with Register C containing the number of characters in the extension.

“MOVE3”
559C

LD B,04H

Let Register B equal 04H, which is the number of characters in an extension (including the delimeter).

“MOVE30”
559E

LD A,(DE)

Fetch a character (held in the memory location pointed to by Register Pair DE) and store it into Register A.

559F

LD (HL),A

Store the character (held in Register A) into the memory location pointed to by Register Pair HL.

55A0

INC C

INCrement the counter (Register C) by 1.

55A1

INC HL

INCrement the pointer for the destination (stored in Register Pair HL) by 1.

55A2

INC DE

INCrement the pointer for the source (stored in Register Pair DE) by 1.

55A3

DJNZ MOVE30
[559EH]

LOOP back to 559EH for up to 4 iterations, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

55A5

RET

RETurn to the caller.

55A6H – Routine to the drivespec from the directory entry (pointed to by DE) into the DCB (pointed to HL).

“MOVE4”
55A6

LD B,03H

Let Register B equal 03H, for a count of 3 characters.

“MOVE40”
55A8

LD A,(DE)

Fetch a character (held in the memory location pointed to by Register Pair DE) and store it into Register A.

55A9

LD (HL),A

Store the character (held in Register A) into the memory location pointed to by Register Pair HL.

55AA

INC HL

INCrement the pointer for the destination (stored in Register Pair HL) by 1.

55AB

INC DE

INCrement the pointer for the source (stored in Register Pair DE) by 1.

55AC

DJNZ 55A8H
[55A8H]

LOOP back to 55A8H for up to 3 iterations, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

55AE

RET

RETurn to the caller.

55AFH – Routine to Skip Spaces in DE and Point to the next Non-Blank Character.

“SKSP”
55AF

LD A,(DE)

Fetch a character (held in the memory location pointed to by Register Pair DE) and store it into Register A.

55B0

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE).

55B2

RET NZ

If the NZ FLAG (Not Zero) has been set, RETurn to the caller.

55B3

INC DE

INCrement the pointer for the source (stored in Register Pair DE) by 1.

55B4

JR SKSP
[55AFH]

Loop back to 55AFH to keep parsing.

55B6H – This routine gets called if the user entered a wildcard copy command such as “COPY /EXT:x :x”.

“SLANT”
55B6

INC DE

INCrement the command line pointer (stored in Register Pair DE) by 1.

55B7

LD IX,S9CMD

Let Special Index Register Pair IX equal the extension storage area of 5562H.

55BB

LD B,03H

Let Register B equal 03H, the length of an extension without the “/” delimeter.

55BD

CALL MOVE1
[557CH]

Transfer characters the number of characters held in Register B from (DE) to (IX), aborting if a SPACE is found via a GOSUB to 557CH.

55C0

LD A,(DE)

Fetch the next character from the COMMAND LINE (held in the memory location pointed to by Register Pair DE) and store it into Register A.

55C1

CP 3AH

Compare the value held in Register A against 3AH (ASCII: :). Results: If Register A equals :, the Z FLAG is set; otherwise the NZ FLAG is set.

55C3

JP NZ,ERR2
[5219H]

If we got a “:” then are good; but if we didn’t then the NZ FLAG (Not Zero) will have been set, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

55C6

LD IX,DRIVE1

Let Special Index Register Pair IX point to the read drive save area.

55CA

LD B,02H

Let Register B equal 02H to move 2 characters (:d).

55CC

CALL MOVE1
[557CH]

Get the SOURCE filespec by transfering characters the number of characters held in Register B from (DE) to (IX), aborting if a SPACE is found via a GOSUB to 557CH.

55CF

CALL SKSP
[55AFH]

GOSUB to 55AFH to skip spaces pointed to by Register Pair DE and point to the next Non-Blank character pointed to by Register Pair DE.

55D2

CP 3AH

Compare the value held in Register A against 3AH (ASCII: :). Results: If Register A equals :, the Z FLAG is set; otherwise the NZ FLAG is set.

55D4

JP NZ,ERR2
[5219H]

If we got a “:” then are good; but if we didn’t then the NZ FLAG (Not Zero) will have been set, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

55D7

LD IX,DRIVE2

Let Special Index Register Pair IX point to the destination drive save area.

55DB

LD B,02H

Let Register B equal 02H to move 2 characters (:d).

55DD

CALL MOVE1
[557CH]

Transfer characters the number of characters held in Register B from (DE) to (IX), aborting if a SPACE is found via a GOSUB to 557CH.

55E0

LD A,(DRIVE2+1)

Fetch the 2nd character pointing to the destination drive save area (held in memory location 555FH) and store it into Register A.

55E3

CP 34H

Compare the value held in Register A against 34H (ASCII: 4). Results:

If Register A equals 4, the Z FLAG is set.
If A < 4, the CARRY FLAG will be set.
if A >= 4, the NO CARRY FLAG will be set.

55E5

JP NC,5221H
[5221H]

If the destination drive is greater than or equal to A >= 4, we have a bad drive, and the If the NC FLAG (No Carry) will have been set, JUMP to 5221H to report the error “Drive not in System” and abort.

55E8H – Common Routine for COPY and KILL – Wild Card Search Routine.

“SLANT0”
55E8

LD A,03H

Let Register A equal 03H to point to the beginning of the directory, which is sector 3 of the directory track.

55EA

LD (S9TRK),A

Store the value held in Register A (i.e., 03H) into the memory location (5567H) which holds the directory sector we want to read.

55ED

LD A,(DRIVE1+1)

Fetch the READ DRIVE DRIVE NUMBER (held in memory location 555CH) and store it into Register A.

55F0

CP 34H

Compare the value held in Register A against 34H (ASCII: 4). Results:

If Register A equals 4, the Z FLAG is set.
If A < 4, the CARRY FLAG will be set.
if A >= 4, the NO CARRY FLAG will be set.

55F2

JP NC,5221H
[5221H]

If the source drive is greater than or equal to A >= 4, we have a bad drive, and the If the NC FLAG (No Carry) will have been set, JUMP to 5221H to report the error “Drive not in System” and abort.

55F5

LD B,10H

Let Register B equal 10H (Decimal: 16), which is the number of directory records, so that Register B can act as a counter.

“TOTAL”
55F7

PUSH BC

Save the counter (held in Register Pair BC) to the top of the stack.

55F8

CALL GETDIR
[5568H]

Read the Directory into 4300H via a GOSUB to 5568H.

55FB

LD DE,4300H

Let Register Pair DE equal 4300H to point to the start of the directory sector in RAM.

55FE

LD (SAVE3),DE

Store the buffer start pointer (held in Register Pair DE) into memory location 5565H.

“TOTAL0”
5602

LD A,(DE)

Fetch a character from directory (held in the memory location pointed to by Register Pair DE) and store it into Register A.

5603

CP 10H

Compare the value held in Register A against 10H (0001 0000) to see if it is protected in any way. Results: If Register A equals 10H, the Z FLAG is set; otherwise the NZ FLAG is set.

5605

JR NZ,TOTNXT
[564EH]

If the file is protected, then the NZ FLAG (Not Zero) will have been set, so skip this file by JUMPing to 564EH.

If we are here, then the file CAN be copied or killed, next we need to see if the user supplied extension matches the filename’s extension.

5607

LD A,E

Copy the LSB of the directory pointer (held in Register E) into Register A.

5608

ADD A,0DH

LET Register A = Register A + 0DH so as to now point to the filename extension of the current file.

560A

LD E,A

Copy the poiner to the extent (held in Register A) back into Register E.

560B

LD HL,S9CMD

Let Register Pair HL point to the user requested filename extension held at 5562H.

560E

LD B,03H

Let Register B equal 03H to prepare for 3 characters, as we need to compare the user requested exension against the extension of the current file.

“TOTAL1”
5610

LD A,(DE)

Fetch a character from the file’s extension from the directory (held in the memory location pointed to by Register Pair DE) and store it into Register A.

5611

CP (HL)

Compare the character from the file’s extension from the directory (held in Register A) against the value requested by the user (held in the memory location pointed to by the value held in Register Pair HL). Results: If Register they match, the Z FLAG is set; otherwise the NZ FLAG is set.

5612

JP NZ,TOTNXT
[564EH]

If the don’t match, then the NZ FLAG (Not Zero) will have been set, and we will want to skip this file by JUMP to 564EH.

5615

INC DE

INCrement the pointer to the character from the file’s extension from the directory (stored in Register Pair DE) by 1.

5616

INC HL

INCrement the pointer to the character from the user specified extension (stored in Register Pair HL) by 1.

5617

DJNZ TOTAL1
[5610H]

Keep checking the 3 extension characters by LOOPing back to 5610H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5619

LD DE,(SAVE3)

If we’re here, the user extension matched the current filename in the directory’s extension so fetch the buffer pointer (held in memory location 5565H) and store it into Register Pair DE.

561D

LD A,E

Copy the LSB of the directory pointer (held in Register E) into Register A.

561E

ADD A,05H

LET Register A = Register A + 05H so as to point to the file’s filespec.

5620

LD E,A

Put the LSB of the directory pointer, now pointing to the name, back into Register E.

5621

LD C,00H

Let Register C equal 00H so that Register C can be a counter.

5623

LD HL,S9DCB1

Let Register Pair HL equal equal 6162H which is the beginning of the SOURCE FILE DCB.

5626

CALL MOVE2
[558FH]

Copy a filename from the directory entry (pointed to by DE) into the DCB (pointed to HL) via a GOSUB to 558FH. Returns with Register C containing the number of characters in the filename.

5629

LD DE,ZSLANT

Let Register Pair DE equal 5561H, which is the pointer to the RAM SAVE area for the extension, starting with the “/”.

562C

CALL MOVE3
[559CH]

Attach the extension to the file filename via a GOSUB to 559CH.

562F

PUSH BC

Save the counter/length of the filespec (held in Register Pair BC) to the top of the stack.

5630

LD DE,DRIVE1

Let Register Pair DE equal 555BH to point to the SOURCE FILE drivespec.

5633

CALL MOVE4
[55A6H]

Attach the drivespec to the filename via a GOSUB to 55A6H.

5636

LD HL,S9DCB1

Let Register Pair HL equal equal 6162H which is the beginning of the SOURCE FILE DCB (which starts with the filename).

5639

LD DE,S9DCB2

Let Register Pair DE equal 6194H to point to the DESTINATION FILE DCB (which starts with the filename).

563C

POP BC

Fetch the counter/length of the filespec from the the top of the STACK into Register Pair BC, and then remove the entry from the stack.

563D

LD B,00H

In preparation for a LDIR, Register Pair BC needs to be set up. Right now only Register C is set up. So here we set Register B to equal 00H to set the MSB of the length so that BC is now the length of the filespec.

563F

LDIR

Copy the filespec from the SOURCE FILE DCB to the DESTINATION FILE DCB via LDIR, which transfers a byte of data from the memory location pointed to by HL to the memory location pointed to by DE. Then HL and DE are incremented and BC is decremented. If BC is not zero, this operation is repeated. Interrupts can trigger while this instruction is processing.

5641

EX DE,HL

EXchange the value stored in Register Pair HL (i.e., the end of the filename in the SOURCE FILE DCB) with the value stored in Register Pair DE (i.e., the end of the filename in the DESTINATION FILE DCB).

5642

LD DE,DRIVE2

Let Register Pair DE equal the DESTINATION FILE DRIVESPEC (held in 555EH).

5645

CALL MOVE4
[55A6H]

Attach the drivespec to the filename via a GOSUB to 55A6H.

5648

CALL COPY0
[54D0H]

Copy/Kill (as set) the file via a GOSUB to 54D0H (COPY) or 5692H (KILL).

564B

CALL GETDIR
[5568H]

Read the Directory into 4300H via a GOSUB to 5568H.

“TOTNXT”
564E

LD DE,(SAVE3)

Fetch the applicable buffer address for the current location in the directory sector (held in memory location 5565H) and store it into Register Pair DE.

5652
5653
5654

LD A,E
ADD A,30H
LD E,A

Advance 30 bytes in the buffer of the sector, thus moving to the next directory entry.

5656

LD (SAVE3),DE

Store the current location in the current directory sector (held in Register Pair DE) into memory location 5565H (which is a storage area for the current buffer address).

565A

CP 0F0H

Check for the end of directory sector location by comparing the first byte of the current directory sector entry (held in Register A) against 0F0H. Results:

If Register A equals 0F0H, the Z FLAG is set.
If A < 0F0H, the CARRY FLAG will be set.
if A >= 0F0H, the NO CARRY FLAG will be set.

565C

JR C,TOTAL0
[5602H]

If A < 0F0H (meaning we are at the end of the directory sector) then the C FLAG (Carry) has been set, JUMP to 5602H to loop to the next sector.

565E

POP BC

Fetch the sector counter (held at the top of the STACK) into Register Pair BC, and then remove the entry from the stack.

565F

LD A,(S9TRK)

Fetch the sector number (held in memory location 5567H) and store it into Register A.

5662

INC A

INCrement the value stored in Register A by 1 so as to point to the next sector.

5663

LD (S9TRK),A

Store the bumped sector number (held in Register A) into memory location 5567H.

5666

DJNZ TOTAL
[55F7H]

Process the entire directory track by LOOPing back to 55F7H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5668

RET

RETurn to the caller.

5669H – “KILL” Routine.

“S9KILL”
5669
566A

LD D,H
LD E,L

LET Register Pair DE = Register Pair HL (the pointer to the COMMAND LINE).

566B

LD A,(DE)

Fetch the first character held on the command line (in the memory location pointed to by Register Pair DE) and store it into Register A.

566C

CP 2FH

Compare the value held in Register A against 2FH (ASCII: /). Results: If Register A equals /, the Z FLAG is set; otherwise the NZ FLAG is set.

566E

JR NZ,5697H
[5697H]

If the first characer is NOT a /, then NZ FLAG (Not Zero) will have been set, and the user is NOT using a wildcard. JUMP to 5697H.

If we are here, then the user requested to KILL based on a WILDCARD.

5670

INC DE

INCrement the value stored in Register Pair DE by 1 to point to the second character from the COMMAND LINE.

5671

LD IX,S9CMD

Let Special Index Register Pair IX equal the extension storage area of 5562H.

5675

LD B,03H

Let Register B equal 03H to move 3 characters.

5677

CALL MOVE1
[557CH]

Transfer characters the number of characters held in Register B from (DE) to (IX), aborting if a SPACE is found via a GOSUB to 557CH.

567A

LD A,(DE)

Fetch the next character from the COMMAND LINE (held in the memory location pointed to by Register Pair DE) and store it into Register A.

567B

CP 3AH

Compare the value held in Register A against 3AH (ASCII: :). Results: If Register A equals 3AH :, the Z FLAG is set; otherwise the NZ FLAG is set.

567D

JP NZ,ERR2
[5219H]

We needed a :. If we didn’t get one, then the the NZ FLAG (Not Zero) will have been set, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5680

LD IX,DRIVE1

Let Special Index Register Pair IX point to the SOURCE DRIVESPEC (555BH).

5684

LD B,02H

Let Register B equal 02H for a move of 2 drivespec characters.

5686

CALL MOVE1
[557CH]

Transfer characters the number of characters held in Register B from (DE) to (IX), aborting if a SPACE is found via a GOSUB to 557CH.

5689

LD HL,KILLIT

Set the vector to the action in the directory entry loop routine to “KILL” by first letting Register Pair HL equal 5692H (which is in the middle of a multi-purporse CALL routine).

568C

LD (TOTCHG + 1),HL

Store the value held in Register HL into the memory location 5649H, which is in the middle of a CALL OPCODE. This will set that OPCODE to “KILL”. The alternative would be from the “COPY” routine, which would set this to a different address.

568F

JP SLANT0
[55E8H]

Proceed to KILL the filed by JUMPing to 55E8H.

5692H – Continuation of the KILL ROUTINE.

“KILLIT”
5692

CALL GETDCB
[59ADH]

GOSUB to 59ADH to set up for FULL SECTOR I/O and sets up registers B, DE, and HL for file action.

5695

JR KILL0
[569DH]

JUMP to 569DH to kill the file.

5697H – Continuation of the KILL ROUTINE; display the KILLING message and kill the file.

“KILL1”
5697

CALL GETSYN
[59BCH]

Process the filespec (i.e., set Register Pair DE to point to the SOURCE FILE DCB, check the syntax of the associated Filespec, and RETurn) via a GOSUB to 59BCH.

569A

JP NZ,ERR3
[521DH]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 521DH.

“”
569D

PUSH HL

Save the contents of Register Pair HL to the top of the stack.

569E

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

569F

LD HL,KILMSG

Let Register Pair HL equal 56BAH, to point to the message “‘KILLING ‘“.

56A2

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

56A5

LD HL,S9DCB1

Let Register Pair HL equal 6162H which is the beginning of the SOURCE FILE DCB, which is also the filespec.

56A8

CALL PRNTIT
[5310H]

Display the filespec after the , to point to the message “‘KILLING ‘“. message via a GOSUB to 5310H.

56AB

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

56AC

POP HL

Put the value held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

56AD

CALL 4424H
[4424H]

Open the file via a GOSUB to 4424H.
NOTE: 4424H is the SYS00/SYS routine to OPEN A DISK FILE for use. This RST 28H’s with a value of 92H so as to call ROUTINE 1 in OVERLAY 3.

56B0

JP NZ,ERRX
[5223H]

If the NZ FLAG (Not Zero) has been set, then that CALL returned an error; report the error and abort via a JUMP to 5223H.

56B3

CALL 442CH
[442CH]

Kill the file via a GOSUB to 442CH.

56B6

JP NZ,ERRX
[5223H]

If the NZ FLAG (Not Zero) has been set, then that CALL returned an error; report the error and abort via a JUMP to 5223H.

56B9

RET

RETurn to the caller.

56BAH – MESSAGE and STORAGE AREA for KILL.

“KILMSG”
56BA

DEFM →

“1DH + 1EH + ‘KILLING ‘ + 03H” Message.

56BAH – MESSAGE and STORAGE AREA for PATCH.

“ADDD”
56C5

DEFM →

“04H + ‘ADD=’” message, which is the address label for the PATCH command.

“FINDD”
56CA

DEFM →

“05H + ‘FIND=’” message, which is the find field label for the PATCH command.

“CHGG”
56D0

DEFM →

“04H + ‘CHG=’” message, which is the new record label for the PATCH command.

“ADD1”
56D5

DEFW 00H

Shared storage byte for either the logical record length (for COPY) or the patch address (for PATCH).

“?????”
56D6

DEFB 00H 00H 00H

Storage for 3 byte EOF

“?????”
56D7

DEFB 00H

Length of FIND FIELD in bytes

“FIND”
56D8

DEFS 32

FIND FIELD Storage Area. The first byte, like above, is the length of the data. The remaining 31 bytes is the data.

“CHAG99”
56F8

DEFS 32

CHANGE FIELD Storage Area. The first byte, like above, is the length of the data. The remaining 31 bytes is the data.

“FNDFLG”
5718

DEFB 00H

“Requested Address Found ” Flag

“ERNSAV”
5719

DEFB 00H

EOF Sector Number

571BH – PATCH Main Routine.

“PATCH”
571B

LD A,(HL)

Fetch the first character of the COMMAND LINE (held in the memory location pointed to by Register Pair HL) and store it into Register A.

571C

CP 2AH

Compare the value held in Register A against 2AH (ASCII: *). Results: If Register A equals *, the Z FLAG is set; otherwise the NZ FLAG is set.

571E

JP Z,HSYS
[58FEH]

If the character was a *, then the Z FLAG (Zero) would have been set, and the user requested to patch a SYSTEM file; so JUMP to 58FEH.

5721

CALL GETSYN
[59BCH]

If we are here, then the user wants to patch a user file (and a filename would be needed). Process the COMMAND LINE filename (i.e., set Register Pair DE to point to the SOURCE FILE DCB, check the syntax of the associated Filespec, and RETurn) via a GOSUB to 59BCH.

5724

JP NZ,ERR3
[521DH]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 521DH.

“PAT0”
5727

CALL SKIPSP
[5F8EH]

Get the next non-space COMMAND LINE character via a GOSUB to 5F8EH.

572A

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN, the Z FLAG is set; otherwise the NZ FLAG is set.

572C

JP Z,ERR3
[521DH]

If the next character was an CARRIAGE RETURN then the Z FLAG (Zero) will have been set, and we didn’t get enough information. Exit with an error via a JUMP to 521DH.

572F

CP 28H

Compare the value held in Register A against 28H (ASCII: (). Results: If Register A equals (, the Z FLAG is set; otherwise the NZ FLAG is set.

5731

JP NZ,ERR2
[5219H]

If the next character wasn’t a (, the NZ FLAG (Not Zero) will have been set, and we did not get the character we needed to proceed. JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5734

INC HL

INCrement the value stored in Register Pair HL by 1 so as to point to the first character after the parenthesis.

5735

LD DE,ADDD

Point DE to the parameter table in RAM by setting Register Pair DE to equal 56C5H, which is the start of the PATCH routine lookup area, and points to the “ADD=” message.

5738

LD A,(DE)

That table is broken down into a byte for the length of the message, and then the message. Fetch the value held in the memory location pointed to by Register Pair DE, which will be the length of the “ADD=” label, and store it into Register A.

5739
573A

LD C,A
LD B,00H

Let Register Pair BC = the length of the “ADD=” label (which is 04H).

573C

INC DE

Point Register Pair DE to the next byte in the table (i.e., the beginning of the message “ADD=”).

573D

CALL COMPAR
[5B70H]

Check to see if the command line paramter matches the label set in DE (in this case, checking to see if the user’s next command letters were “ADD=”) via a GOSUB to 5B70H.

5740

JP NZ,ERR2
[5219H]

If the user didn’t have “ADD=” as the next characters the NZ FLAG (Not Zero) will have been set, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5743

ADD HL,BC

Advance the pointer to the command line (i.e., Register Pair HL) to the end of that label by letting Register Pair HL = Register Pair HL (the current position on the COMMAND LINE) + Register BC (the length of the label we just checked).

5744

PUSH HL

We are now going to need to parse for a value, so save the contents of Register Pair HL (i.e., the pointer to the characters following the “ADD=” label on the command line) to the top of the stack.

5745

POP IX

Restore HL into Register Pair IX.

5747

LD HL,0000H

Let Register Pair HL equal 0000H as a base for math.

“PLOOP1”
574A

LD A,(IX+00H)

Fetch the first character of the address to be patched (held in the memory location pointed to by Special Index Register Pair IX+00H) and store it into Register A.
Note: IX+00H = the position in the DCB for the TYPE of FCB byte. Bit 0: 1=Read Only, Bit 1: 1=Write Only, Bit 4: 1=The next 2 bytes are simply the address of another FCB, Bit 7=1: Then the next 50 bytes are the description of an open file.

The next few instructions compare the character to 0, : (i.e., 1 above 9), A, and G (i.e., 1 above F) to make sure that it is in the range of a valid hex character.

574D

CP 30H

Compare the value held in Register A against 30H (ASCII: 0). Results:

If Register A equals 0, the Z FLAG is set.
If A < 0, the CARRY FLAG will be set.
if A >= 0, the NO CARRY FLAG will be set.

574F

JR C,PLOOP3
[5771H]

If A < 0 then the C FLAG (Carry) will have been set to indicate that the character was too low to be a valid hex character (i.e., it is below “0”), JUMP to 5771H.

5751

CP 3AH

Compare the value held in Register A against 3AH (1 more than ASCII: 9). Results:

If Register A equals 1 more than 9, the Z FLAG is set.
If A < 1 more than 9, the CARRY FLAG will be set.
if A >= 1 more than 9, the NO CARRY FLAG will be set.

5753

JR C,PLOOP2
[575DH]

If A < 1 more than 9 then the C FLAG (Carry) will have been set to indicate that the character we got is less than “9” which is good, so JUMP to 575DH.

5755

CP 41H

Compare the value held in Register A against 41H (ASCII: A). Results:

If Register A equals A, the Z FLAG is set.
If A < A, the CARRY FLAG will be set.
if A >= A, the NO CARRY FLAG will be set.

5757

JR C,PLOOP3
[5771H]

If A < A then the C FLAG (Carry) will have been set to indicate that the character was too low to be a valid hex character (i.e., it is below “A” and was not “0”-“9”, JUMP to 5771H.

5759

CP 47H

Compare the value held in Register A against 47H (ASCII: G). Results:

If Register A equals G, the Z FLAG is set.
If A < G, the CARRY FLAG will be set.
if A >= G, the NO CARRY FLAG will be set.

575B

JR NC,PLOOP3
[5771H]

If A >= G then the NC FLAG (No Carry) will have been setto indicate that the character was too high to be a valid hex character (i.e., it is above “F”), JUMP to 5771H.

The next few instructions turn the validated hex character into decimal.

“PLOOP2”
575D
575E
575F
5760

ADD HL,HL
ADD HL,HL
ADD HL,HL
ADD HL,HL

Shift the old address four bits to the left

5761

SUB 30H

SUBtract the value 30H from Register A. Note: Subtracting 30H from from Register A will convert an ASCII number ‘0’-‘9’ to its decimal equivalent (i.e., 6 in ASCII is 36H in Hex; so 36H-30H = 6).

5763

CP 0AH

Compare the value held in Register A against 0AH (Decimal: 10). Results:

If Register A equals 10, the Z FLAG is set.
If A < 10, the CARRY FLAG will be set.
if A >= 10, the NO CARRY FLAG will be set.

5765

JR C,PLOP2
[5769H]

If A < 10 then the C FLAG (Carry) will have been set and we are done converting the character, so JUMP to 5769H.

5767

SUB 07H

SUBtract the value 07H from Register A which will reduce an ASCII character in the range of “A”-“F” into 11-15.

The parameter character is now a decimal number held in Register A.

“”
5769

LD E,A

At this point, Register A now is the decimal equivalent of the 2 characters given. Copy the contents of Register A into Register E.

576A

LD D,00H

Let Register D equal 00H so that Register Pair DE = Register A.

576C

ADD HL,DE

LET Register Pair HL = the old character address value (held in Register Pair HL) + the new value (held in Register Pair DE).

576D

INC IX

INCrement the value stored in Special Index Register IX by 1 to point to the next digit/character in the ADD= field in the command line.

576F

JR PLOOP1
[574AH]

LOOP BACK to 574AH until the end of the parameter is reached.

5771H – Continuation of the PATCH command. Jumped here if we were given an invalid hex character on the ADD= portion of the command line. A is holding the character from the COMMAND LINE which we know is NOT a valid hex character.

“PLOOP3”
5771

LD (ADD1),HL

Store the address (held in Register Pair HL) into the desingated memory location to hold the patch address (i.e., 56D5H).

5774

CP 2CH

Compare the value held in Register A against a ,. Results: If Register A equals ,, the Z FLAG is set; otherwise the NZ FLAG is set.

5776

JP NZ,ERR2
[5219H]

If the current character is not a , then the NZ flag would have been set and we have an invalid character. JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5779

PUSH IX
POP HL

Let Register Pair HL = Special Index Register IX (which is the command line).

577C

INC HL

Skip over the “,” on the command line by pointing to the next character on the COMMAND LINE by INCrementing the value stored in Register Pair HL by 1.

577D

LD DE,FINDD

Let Register Pair DE equal 56CAH, which is in the PATCH routine lookup area, and points to the “FIND=” message.

5780

LD A,(DE)

Fetch the first byte at that message, which is the length of the “FIND=” command (i.e., 5) and store it into Register A.

5781

INC DE

Move past the length byte to the message by INCrementing the value stored in Register Pair DE by 1. DE now points to the “FIND=” text.

5782
5783

LD C,A
LD B,00H

Set Register Pair BC = the length of the “FIND=” text (i.e., 5 characters)

5785

CALL COMPAR
[5B70H]

Check to see if the command line parameter matches the label set in DE (in this case, checking to see if the user’s next command letters were “ADD=”) via a GOSUB to 5B70H.

5788

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the user label didn’t match the required “FIND=” label, which is bad, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

578B

ADD HL,BC

Advance Register Pair HL to the user provided value associated with a “FIND=” lead in by setting Register Pair HL = the current location on the COMMAND LINE (held in Register Pair HL) + the length of the text “FIND=” (held in Register BC).

578C

LD DE,FIND + 1

Let Register Pair DE equal 56D8H to point to the FIND FIELD storage buffer of 31 characters.

578F

CALL MOVLTH
[58C0H]

Decode the FIND FIELD input via a GOSUB to 58C0H. Routine returns with DE pointing to the converted field and Register A holding the length of the field.

5792

LD (FIND),A

Store the length of the “FIND=” field (i.e., 5 characters; held in Register A) into memory location 56D7H.

5795

LD A,(HL)

Fetch the next character on the command line (in the memory location pointed to by Register Pair HL) and store it into Register A.

5796

CP 2CH

Compare the value held in Register A against a ,. Results: If Register A equals ,, the Z FLAG is set; otherwise the NZ FLAG is set.

5798

JP NZ,ERR2
[5219H]

If the current character is not a , then the NZ flag would have been set and we have an invalid character. JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

579B

INC HL

If we’re here then we got the “,” and are still working on a valid command line. Point HL to the next character on the command line.

579C

LD DE,CHGG

Let Register Pair DE equal 56D0H, which is in the PATCH routine lookup area, and points to the “CHG=” message.

579F

LD A,(DE)

Fetch the first byte at that message, which is the length of the “CHG=” command (i.e., 4) and store it into Register A.

57A0

INC DE

INCrement the value stored in Register Pair DE by 1 to now point to the “CHG=” text.

57A1
57A2

LD C,A
LD B,00H

Set Register Pair BC = the length of the “CHG=” text (i.e., 4 characters)

57A4

CALL COMPAR
[5B70H]

Check to see if the command line paramter matches the label set in DE (in this case, checking to see if the user’s next command letters were “ADD=”) via a GOSUB to 5B70H.

57A7

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the user label didn’t match the required “CHG=” label, which is bad, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

57AA

ADD HL,BC

Advance Register Pair HL to the user provided value associated with a “CHG=” lead in by setting Register Pair HL = the current location on the COMMAND LINE (held in Register Pair HL) + the length of the text “FIND=” (held in Register BC).

57AB

LD DE,CHAG99+1

Let Register Pair DE equal 56F8H to point to the CHANGE FIELD storage buffer of 31 characters.

57AE

CALL MOVLTH
[58C0H]

Decode the CHANGE FIELD input via a GOSUB to 58C0H. Routine returns with DE pointing to the converted field and Register A holding the length of the field.

57B1

LD (CHAG99),A

Store the the length of the given change field (held in Register A after the CALL to 58C0H) into memory location 56F7H.

57B4

LD B,A

Let Register B = the length of the given change field (held in Register A after the CALL to 58C0H).

57B5

LD A,(FIND)

Fetch the length of the given find field (held in memory location 56D7H) and store it into Register A.

57B8

CP B

Check to see if the length of the FIND field (held in Register A) and the length of the CHANGE field (held in Register B) are the same. Results: If Register A equals the value held in Register B, the Z FLAG is set; otherwise the NZ FLAG is set.

57B9

JP NZ,ERR2
[5219H]

If they FIND and CHG fields were not the same length, the NZ FLAG (Not Zero) will have been set. JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

If we are here, then we have the FIND field and the CHANGE fields stored and they are of matching length.

57BC

XOR A

Set Register A to ZERO and clear all Flags so that we can put a 00H into some memory locations.

57BD

LD (CHGFLG),A

Store the value held in Register A into memory location 5717H (which points to the CHANGE REQUIRED flag).

57C0

LD (FNDFLG),A

Store the value held in Register A into memory location 5718H (which points to the ADDRESS FOUND flag).

57C3

LD A,(SYSFLG)

Fetch the value held in memory location 599AH (i.e., the SYSTEM OVERLAY FLAG for the PATCH routine; NZ if system file being patched) and store it into Register A.

57C6

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

57C7

JR NZ,PATL00
[57D8H]

If patching file overlay system then we are going to want to skip the FILE OPEN portion of this routine, JUMP to 57D8H.

57C9
57CC

LD IYL, 0FFH
LD IYH, 42H

Open the file. First … Set the Special Index Register IY = 42FFH to point to the protection override flag.

57CF

DEC (IY+00H)

Turn off the password check by DECrementing the value stored in the memory location pointed to by Special Index Register IY+00H by 1.

57D2

CALL OPENIT
[599BH]

OPEN the file via a GOSUB to 599BH.

57D5

JP NZ,ERRX
[5223H]

If the NZ FLAG (Not Zero) has been set, then that CALL returned an error; report the error and abort via a JUMP to 5223H.

“PATL00”
57D8

LD A,(6163H)

Fetch the file status/protection byte (held in memory location 6163H) and store it into Register A.

57DB

AND 0F8H

MASK the value of Register A against 0F8H (1111 1000) to zero out the 3 bytes consisting of the access code, thus granting full access.

57DD

LD (6163H),A

Put the masked file status/protection byte back into memory location 6163H (where the options byte is stored).

57E0

LD HL,(6172H)

Fetch the first extent element (held in memory location 6172H) and store it into Register Pair HL.

57E3

LD A,L

The LSB of the extent element (i.e., Register L) is the track number, so copy the track number (held in Register L) into Register A.

57E4

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

57E5

JR NZ,PATL01
[57F3H]

If we are not at SYS00/SYS, then tne NZ flag will be set, so skip the next few command via a JUMP to 57F3H.

57E7

LD A,H

Let’s double check to make sure we aren’t at SYS00/SYS. First, copy the gran offset into the track (held in the MSB of the extent element; currently in Register H) into Register A.

57E8

AND 0E0H

MASK the value of Register A against 0E0H (1110 0000) to mask off the number of grans.

57EA

JR NZ,PATL01
[57F3H]

If that is still not zero, then the user is not trying to patch OVERLAY 0 then the NZ FLAG (Not Zero) will have been set, so skip the next few command via a JUMP to 57F3H.

57EC

LD A,(616CH)

Fetch the “next sector” number (held in memory location 616CH) and store it into Register A.

57EF

INC A

INCrement the value stored in Register A by 1 so that Register A will never be 0 (and hence, will never patch the BOOT file).

57F0

LD (616CH),A

Store the bumped “next sector” (held in Register A) into the “next sector” memory location of 616CH.

“PATL01”
57F3

CALL REDIT
[58B3H]

Read the first sector via a GOSUB to 58B3H.

57F6

LD BC,(616EH)

Fetch the EOF sector (head in memory location 616EH) and store it into Register Pair BC.

57FA

LD (5719H),BC

Store the EOF sector into memory location 5719H (which is the designated storage location of the EOF sector number).

Next, we need to get a block of data from the file.

“”
57FE

LD A,(HL)

Fetch the byte of data held in the buffer memory location pointed to by Register Pair HL and store it into Register A.

57FF

CP 01H

Compare the value held in Register A against 01H to see if it is a CODE BLOCK. Results: If Register A equals 01H, the Z FLAG is set; otherwise the NZ FLAG is set.

5801

JR Z,PATCHK
[5816H]

If the Z FLAG (Zero) has been set, JUMP to 5816H to process a CODE BLOCK.

5803

CP 02H

Compare the value held in Register A against 02H to see if it is an EXECUTION ADDRESS. Results: If Register A equals 02H, the Z FLAG is set; otherwise the NZ FLAG is set.

5805

JP Z,PATEND
[5897H]

If the Z FLAG (Zero) has been set, JUMP to 5897H to display the results of the Patch.

5808

CP 03H

Compare the value held in Register A against 03H to see if it is an END OF FILE CHARACTER. Results: If Register A equals BREAK, the Z FLAG is set; otherwise the NZ FLAG is set.

580A

JP Z,PATEND
[5897H]

If the Z FLAG (Zero) has been set, JUMP to 5897H to display the results of the Patch.

580D

CP 21H

Compare the value held in Register A against 21H to see if it is a COMMENT BLOCK. Results:

If Register A equals 21H, the Z FLAG is set.
If A < 21H, the CARRY FLAG will be set.
if A >= 21H, the NO CARRY FLAG will be set.

580F

JR C,DLYLOP
[5888H]

If the C FLAG (Carry) has been set, JUMP to 5888H to throw away the comment block.

5811

LD A,22H

If we haven’t jumped away, then we have an invalid block. Let Register A equal 22H to indicate an INVALID FILE FORMAT error.

5813

JP ERRX
[5223H]

Report the error and abort via a JUMP to 5223H.

5816H – Continuation of the PATCH command. Read a CODE BLOCK from the file.

“PATCHK”
5816

INC HL

Point to the next byte in the buffer holding the CODE BLOCK of the file via a bump to Register Pair HL.

5817

LD B,(HL)

Fetch the next byte of the CODE BLOCK, which is the field size/character count, and put that into Register B.

5818

INC HL

Point to the next byte of the CODE BLOCK (the load address) in the file via a bump to Register Pair HL.

5819

LD E,(HL)

Fetch the next byte of the CODE BLOCK, which is the LSB of the LOAD ADDRESS, and put that into Register B.

581A

DEC B

DECrement the field size/character count (held in Register B) by 1 byte.

581B

INC HL

Fetch the next byte of the CODE BLOCK, which is the MSB of the LOAD ADDRESS, and put that into Register B.

581C

LD D,(HL)

Fetch the next byte of the CODE BLOCK, which is the data address MSB, and put that into Register B.

581D

DEC B

DECrement the field size/character count (held in Register B) by 1 byte.

581E

PUSH HL

Save the pointer in the buffer to the current location of the CODE BLOCK (held in Register Pair HL) to the top of the stack.

581F

PUSH DE

Save the LOAD ADDRESS (held in Register Pair DE) to the top of the stack.

5820

JR NZ,PATCH0
[5825H]

If Register B isn’t zero then the NZ FLAG (Not Zero) will have been set, meaning we have more data to read so JUMP to 5825H.

5822

SCF

If we are here then we know the sector is length is not 0 and is not 256, we have an error, so SET the CARRY FLAG to indicate as much.

5823

JR PATCH1
[5828H]

JUMP to 5828H to offset the address.

5825H – Continuation of the PATCH command read a CODE BLOCK routine; jumped here if there is more data to read in the code block than just the 3 bytes comprising the field size and data address.

The next few instructions are to set DE to be DE + the length of the field. This requires some math. First, work the LSB of Register Pair DE.

“PATCH0”
5825
5826
5827

LD A,E
ADD A,B
LD E,A

Let Register E = the data address LSB (which was already in E) plus the data field size – 2.

“PATCH1”
5828
5829
582B

LD A,D
ADC A,00H
LD D,A

Let Register D = the data address MSB (which was already in D) + 1 byte if the addition of the LSB produced a carry.

582C

LD HL,(ADD1)

Fetch the user requested patch address from its storage place (in memory location 56D5H) into Register Pair HL.

582F

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG, which we will need cleared for the next operation).

5830

SBC HL,DE

Subtracts the value stored in Register Pair DE (the size of the patch) and the carry flag from the value stored in Register Pair HL (the block to patch). This will tell us if the patch will be entirely within the single block.

5832

POP DE

Restore the address of the block from the top of the STACK into Register Pair DE, and then remove the entry from the stack.

5833

POP HL

Restore the field size from the top of the STACK into Register Pair HL, and then remove the entry from the stack.

5834

JR NC,DLYLO1
[588AH]

If the NC FLAG (No Carry) has been set then the load address is too low; so JUMP to 588AH.

5836

PUSH HL

Save the field size (held in Register Pair HL) to the top of the stack.

5837

LD HL,(ADD1)

Fetch the patch address from its storage place (in memory location 56D5H) into Register Pair HL.

583A

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

583B

SBC HL,DE

Put the offset into the block inter Register Pair HL by subtracting the address of the block (stored in Register Pair DE) and the carry flag from the patch address (stored in Register Pair HL).

583D

LD B,L

Copy the LSB of the offset into the block (held in Register L) into Register B.

583E

POP HL

Restore the field size from the top of the STACK into Register Pair HL, and then remove the entry from the stack.

583F

JR C,DLYLO1
[588AH]

If the subtraction triggered the CARRY FLAG, then we need to redo the math to see if we need to go BEFORE the current block. JUMP to 588AH.

5841

INC L

Bump Register L to point past the MSB of the LOAD ADDRESS by INCrementing the value stored in Register L by 1.

5842

OR 01H

Since the address has been found, we need to OR Register A against 01H (0000 0001), to force Register A to be anything but a 0 for the next instruction.

5844

LD (FNDFLG),A

Store a non-zero (held in Register A) into memory location 5718H (which points to the ADDRESS FOUND flag).

5847

LD A,B

Copy the byte count offset a/k/a the remaining length (held in Register B) into Register A.

5848

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5849

JR Z,PATCH3
[5851H]

If the Z FLAG (Zero) has been set then we are finally at the data! JUMP to 5851H. Otherwise fall through to keep looping.

“PATCH2”
584B

INC L

If we didn’t jump away, then we are not yet at the data so point to the next byte by INCrementing the value stored in Register L by 1.

584C

CALL Z,REDIT
[58B3H]

If the Z FLAG (Zero) has been set, meaning that L just spilled into the next sector and we ran out of buffer, GOSUB to 58B3H to read the next seector.

584F

DJNZ PATCH2
[584BH]

Keep looping back to 584BH until we get to the requested address, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

“PATCH3”
5851

LD DE,FIND

Let Register Pair DE equal 56D7H, which is the pointer to the storage location for the LENGTH OF THE FIND FIELD.

5854

LD A,(DE)

Fetch the length of the find field from the memory location pointed to by Register Pair DE and store it into Register A.

5855

INC DE

INCrement the value stored in Register Pair DE by 1 so that it now points to the 31 byte storage location for the FIND FIELD.

5856

LD C,A

Copy the field length (held in Register A) into Register C.

5857

LD B,00H

Let Register B equal 00H so that Register Pair BC will hold the field length.

5859

CALL COMPAR
[5B70H]

Check to see if we have found what we are looking for via a GOSUB to 5B70H.

585C

JP NZ,PATERR
[59C2H]

If the NZ FLAG (Not Zero) has been set, then no match was found; JUMP to 59C2H to display a “STRING NOT FOUND” message and ABORT.

585F

LD DE,CHAG99+1

Let Register Pair DE equal 56F8H to point to the CHANGE FIELD storage buffer of 31 characters.

5862

CALL COMPAR
[5B70H]

Check to see if a change is really needed via a GOSUB to 5B70H.

5865

JR Z,PATEND
[5897H]

If the Z FLAG (Zero) has been set then what we wanted to check it to was actually what was there, so JUMP to 5897H to display the results of the patch.

5867

EX DE,HL

EXchange the value stored in Register Pair HL (i.e., the data location to be changed) with the value stored in Register Pair DE (i.e., the CHANGE FIELD storage buffer).

5868

LDIR

Move the new string into the old location via a LDIR instuction, which transfers a byte of data from the memory location pointed to by HL to the memory location pointed to by DE. Then HL and DE are incremented and BC is decremented. If BC is not zero, this operation is repeated. Interrupts can trigger while this instruction is processing.

586A

OR 01H

We need a non-Zero put into the next memory location so OR Register A against 01H (0000 0001) to set the “CHANGE REQUIRED” flag to a non-zero number.

586C

LD (CHGFLG),A

Show that we have now made the requested change by storing the value held in Register A into memory location 5717H (which points to the CHANGE REQUIRED flag).

586F

LD A,(SYSFLG)

Fetch the value held in memory location 599AH (i.e., the SYSTEM OVERLAY FLAG for the PATCH routine; NZ if system file being patched) and store it into Register A.

5872

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5873

PUSH AF

Save the status flags from the check to see if this a SYSTEM FILE to the top of the stack.

5874

CALL NZ,CLOSYS
[5963H]

If the NZ FLAG (Not Zero) has been set then we were working on a SYSTEM FILE, so we need to close it via a GOSUB to 5963H.

5877

POP AF

Restore the status flags into Register Pair AF, and then remove the entry from the stack.

5878

JR NZ,PATEND
[5897H]

If the NZ FLAG (Not Zero) has been set then we were working on a SYSTEM FILE, so exit by JUMPing to 5897H to display the results of the patch.

If we are here, then we just patched a non-SYSTEM file.

587A

CALL GETDCB
[59ADH]

Set up for FILE I/O via a GOSUB to 59ADH to set up for FILL SECTOR I/O and sets up registers B, DE, and HL.

587D

CALL 4445H
[4445H]

Back up to the proper sector via a GOSUB to 4445H.

5880

CALL GETDCB
[59ADH]

Set up for FILE I/O via a GOSUB to 59ADH to set up for FILL SECTOR I/O and sets up registers B, DE, and HL.

5883

CALL 443CH
[443CH]

5886

JR PATEND
[5897H]

JUMP to 5897H to disply the results of the patch and finish.

5888H – Continuation of the PATCH command to deal with a COMMENT BLOCK.

“DLYLOP”
5888

INC HL

Bypass the NO-USE byte and point to the next byte by INCrementing the value stored in Register Pair HL by 1.

5889

LD B,(HL)

Fetch the length byte (held in the memory location pointed to by Register Pair HL) and store it into Register B.

“DLYLO1”
588A

INC L

Point to the next byte by INCrementing the value stored in Register Pair L by 1.

588B

CALL Z,REDIT
[58B3H]

If the Z FLAG (Zero) has been set then we slipped to the next sector and ran out of buffer; so get the next sector via a GOSUB to 58B3H.

588E

DJNZ DLYLO1
[588AH]

Skip the entire comment block (based on the field length byte) via a DJNZ LOOP back to 588AH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5890

INC L

Point to the next byte by INCrementing the value stored in Register Pair L by 1.

5891

CALL Z,REDIT
[58B3H]

If the Z FLAG (Zero) has been set then we slipped to the next sector; so get the next sector via a GOSUB to 58B3H.

5894

JP PATLO0
[57FEH]

JUMP to 57FEH to get the next block.

5897H – Continuation of the PATCH command to display the results of the Patch and exit.

“PATEND”
5897

LD A,(FNDFLG)

See if we found the address by fetching the “Requested Address Found” Flag from where it lives (memory location 5718H) and store it into Register A.

589A

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

589B

JR NZ,PATEN1
[58A3H]

If the NZ FLAG (Not Zero) has been set then we have found the requested address, so JUMP to 58A3H to see if we had to make a change.

589D

LD HL,NOFIND

Let Register Pair HL equal 59E4H to point to the message “SPECIFIED ADDRESS NOT FOUND“.

“PATEN0”
58A0

JP 021BH
[021BH]

JUMP to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found. Since this was JUMPED to instead of CALLed, the RET at the end of this ROM routine will then RETurn to the caller of this subroutine instead of returning to this place.

58A3H – Continuation of the PATCH command to display the results of the Patch if we have a match.

“PATEN1”
58A3

LD A,(CHGFLG)

See if we actually made a change by fetching the value held in memory location 5717H (which points to the CHANGE REQUIRED flag) into Register A.

58A6

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

58A7

JR NZ,PATEN2
[58AEH]

If the NZ FLAG (Not Zero) has been set, then the change field was NOT the same as the found field, which is bad; so skip via a JUMP to 58AEH.

58A9

LD HL,NOCHAG

Let Register Pair HL equal 59E4H to point to the message “NO CHANGE REQUIRED“.

58AC

JR PATEN0
[58A0H]

JUMP to 58A0H to display the message pointed to by Register Pair HL and exit.

58AEH – Continuation of the PATCH command to display the results of a successful Patch.

“PATEN2”
58AE

LD HL,CHGMAD

Let Register Pair HL equal 59C8H to point to the message “PATCH MADE“.

58B1

JR PATEN0
[58A0H]

JUMP to 58A0H to display the message pointed to by Register Pair HL and exit.

58B3H – Continuation of the PATCH command. Subroutine to read a sector.

“REDIT”
58B3

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

58B4

CALL GETDCB
[59ADH]

Set up for FILE I/O via a GOSUB to 59ADH to set up for FILL SECTOR I/O and sets up registers B, DE, and HL.

58B7

CALL 4436H
[4436H]

GOSUB to 4436H.
NOTE: 4436H is the SYS00/SYS vector for ‘READ’, which reads the record that the disk drive is positioned over.

58BA

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

58BB

RET Z

If the Z FLAG (Zero) has been set then there was no error from that GOSUB, so RETurn to the caller.

“REDI0”
58BC

POP HL

If we are here, then there was an error in the read. Clear the stack.

58BD

JP ERRX
[5223H]

Report the error and abort via a JUMP to 5223H.

58C0H – Part of the PATCH routine. This routine decodes an abitrary length hexadecimal field. It is called related to the FIND and CHG fields given by the user. HL points to the source, and DE points to the destination.

“MOVLTH”
58C0

LD B,00H

Let Register B equal 00H as it will be a length counter.

“MOVLT1”
58C2

LD A,(HL)

Fetch the character held in the memory location pointed to by Register Pair HL and store it into Register A.

58C3

CP 30H

Compare the value held in Register A against 30H to see if we got a character less than “0” (i.e., END OF STRING). Results:

If Register A equals 30H, the Z FLAG is set.
If A < 30H, the CARRY FLAG will be set.
if A >= 30H, the NO CARRY FLAG will be set.

58C5

JR C,MOVLT2
[58D7H]

If the C FLAG (Carry) has been set then we are at the end of the string, so JUMP to 58D7H.

58C7

CALL TCONV
[58DDH]

GOSUB to 58DDH to convert the value to HEX (which will sit in the the LEFT NYBBLE).

58CA

LD C,A

Copy the left nybble (held in Register A) into Register C.

58CB

INC HL

Point to the next character in the field by INCrementing the value stored in Register Pair HL by 1.

58CC

LD A,(HL)

Fetch the next character (held in the memory location pointed to by Register Pair HL) and store it into Register A.

58CD

CALL TCONV1
[58E9H]

GOSUB to 58E9H to convert the value to HEX (which will sit in the RIGHT NYBBLE).

58D0

OR C

Combine the LEFT and RIGHT nybbles via an OR. The results are stored in Register A.

58D1

LD (DE),A

Store the combined/derived value (held in Register A) into the memory location pointed to by Register Pair DE.

58D2

INC DE

INCrement the destination pointer to the next slot.

58D3

INC HL

INCrement the source pointer to the next character.

58D4

INC B

INCrement the counter (stored in Register B) by 1.

58D5

JR MOVLT1
[58C2H]

LOOP back to almost the top of this routine at 58C2H.

58D7H – Part of the PATCH routine’s subroutine which decodes an abitrary length hexadecimal field. Jumped here when we hit the END OF STRING (by virtue of a character below “0” being found).

“MOVLT2”
58D7

LD A,B

Copy the found field length (held in Register B as a counter) into Register A.

58D8

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

58D9

JP Z,ERR3
[521DH]

If the Z FLAG (Zero) has been set, the field length was zero and we were therefore missing a parameter, which is bad. JUMP to 521DH to exit with an error.

58DC

RET

RETurn to the caller.

58DDH – Convert a Byte Contaning a Hex Character to the High Nybble.

“TCONV”
58DD

CALL TCONV1
[58E9H]

Get the value of the ASCII character via a GOSUB to 58E9H.

58E0
58E2
58E4
58E6

SLA A
SLA A
SLA A
SLA A

Shift the bits in Register A left FOUR positions (to the MSB), with new bits being filled in with a 0.

58E8

RET

RETurn to the caller.

58E9H – Convert a Byte Contaning a Hex Character to the Low Nybble a/k/a get the value of an ASCII character.

“TCONV1”
58E9

SUB 30H

58EB

JP C,ERR2
[5219H]

If the C FLAG (Carry) has been set then the character is below “0”, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

58EE

CP 0AH

If we’re here then the character is not below “0”. Next compare the value held in Register A against 0AH (Decimal: 10). Results:

If Register A equals 10, the Z FLAG is set.
If A < 10, the CARRY FLAG will be set.
if A >= 10, the NO CARRY FLAG will be set.

58F0

RET C

If the C FLAG (Carry) has been set then the character is less than 10, so we are good! RETurn to the caller.

58F1

SUB 07H

If we’re here then the character is greater than 10. SUBtract the value 07H from Register A since there are 7 characters between “9” and “A”.

58F3

CP 0AH

Compare the value held in Register A against 0AH (Decimal: 10). Results:

If Register A equals 10, the Z FLAG is set.
If A < 10, the CARRY FLAG will be set.
if A >= 10, the NO CARRY FLAG will be set.

58F5

JP C,ERR2
[5219H]

If the C FLAG (Carry) has been set then A < 10 which is too low to be an “A”-“F”, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

58F8

CP 10H

Compare the value held in Register A against 10H (Decimal: 16). Results:

If Register A equals 16, the Z FLAG is set.
If A < 16, the CARRY FLAG will be set.
if A >= 16, the NO CARRY FLAG will be set.

58FA

RET C

If If A < 16 the C FLAG (Carry) will have been set and we have a good character, RETurn to the caller.

58FB

JP ERR2
[5219H]

JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

58FEH – PATCH routine for a SYSTEM/OVERLAY File.

“HSYS”
58FE

INC HL

INCrement the pointer to the COMMAND LINE (stored in Register Pair HL) by 1; this should be a value.

58FF

CALL HEXGET
[597BH]

Get the overlay number (following the “*” we just got) via a GOSUB to 597BH. Response in Register Pair DE.

5902

PUSH DE

Save the overlay number from that GOSUB (held in Register Pair DE) to the top of the stack.

5903

CALL SKIPSP
[5F8EH]

Get the next COMMAND LINE character (skipping spaces) via a GOSUB to 5F8EH.

5906

LD C,00H

Let Register C equal 00H for a default drivespec of 0.

5908

CP 3AH

Compare the value held in Register A against 3AH (ASCII: :). Results: If Register A equals :, the Z FLAG is set; otherwise the NZ FLAG is set.

590A

JR NZ,HSYS1
[5915H]

If we did not get a : then we are not getting a drive number, so skip the next few instructions which would seek to interpret the command line for a drive number and JUMP to 5915H.

590C

INC HL

INCrement the pointer to the COMMAND LINE (stored in Register Pair HL) by 1 to point to the ASCII drive number.

590D

LD A,(HL)

Fetch the drive number (the next character from the COMMAND LINE; held in the memory location pointed to by Register Pair HL) and store it into Register A.

590E

INC HL

INCrement the pointer to the COMMAND LINE (stored in Register Pair HL) by 1 to move past the ASCII drive number.

590F

SUB 30H

SUBtract the value 30H from Register A (which is supposed to hold a drive number). Note: Subtracting 30H from from Register A will convert an ASCII number ‘0’-‘9’ to its decimal equivalent (i.e., 6 in ASCII is 36H in Hex; so 36H-30H = 6).

5911

JP C,ERR2
[5219H]

If the number is too low then the C FLAG (Carry) will have been set, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5914

LD C,A

Copy the drive number in binary form (held in Register A) into Register C.

“HSYS1”
5915

EX (SP),HL

EXchange the value stored in Register Pair HL (the pointer to the current letter on the COMMAND LINE) with the value stored at the top of stack (i.e., the system overlay number).

5916

PUSH HL

Save the overlay number (held in Register Pair HL) to the top of the stack.

5917

PUSH BC

Save the drive number (held in Register Pair BC) to the top of the stack.

5918

LD HL,S9DCB1

Let Register Pair HL equal 6162H which is the beginning of the SOURCE FILE DCB.

591B

LD DE,S9DCB1+1

Let Register Pair DE equal the second byte of the SOURCE FILE DCB.

591E

LD BC,0031H

Let Register Pair BC equal 0031H for the size of a DCB (i.e., 49) bytes to move.

5921

LD (HL),00H

Store the value held in 00H into the memory location pointed to by Register Pair HL so that the LDIR will zero out everything.

5923

LDIR

5925

LD IX,S9DCB1

Let Special Index Register Pair IX equal 6162H which is the beginning of the SOURCE FILE DCB.

5929

LD (IX+00H),80H

Set IX+00H to 80H (1000 0000)to indicate that the file is open.
Note: IX+00H = the position in the DCB for the TYPE of FCB byte. Bit 0: 1=Read Only, Bit 1: 1=Write Only, Bit 4: 1=The next 2 bytes are simply the address of another FCB, Bit 7=1: Then the next 50 bytes are the description of an open file.

592D

LD (IX+0CH),0FFH

Store a 0FFH (i.e., indefinite) into the memory location pointed to by Special Index Register Pair IX+0CH.
Note: IX+0CH = the position in the DCB for the NMSB OF THE LAST SECTOR TO READ/EOF)

5931

LD (IX+0DH),0FFH

Store a 0FFH (i.e., indefinite) into the memory location pointed to by Special Index Register Pair IX+0DH.
Note: IX+0DH = the position in the DCB for the MSB OF THE LAST SECTOR TO READ/EOF)

5935

LD (IX+03H),00H

Store the value held in 00H into the memory location pointed to by Special Index Register Pair IX+03H.
Note: IX+03H = the position in the DCB for the LSB of the FILE BUFFER RAM ADDRESS).

5939

LD (IX+04H),63H

Store the value held in 63H into the memory location pointed to by Special Index Register Pair IX+04H.
Note: IX+04H = the position in the DCB for the MSB of the FILE BUFFER RAM ADDRESS).

593D

POP BC

Put the drive number (held at the top of the STACK) into Register Pair BC, and then remove the entry from the stack.

593E

LD (IX+06H),C

Store the drive number (held in Register C) into the memory location pointed to by Special Index Register Pair IX+06H.
Note: IX+06H = the position in the DCB for the DRIVE NUMBER).

5941

POP DE

Restore the overlay number from the top of the STACK into Register Pair DE, and then remove the entry from the stack.

5942

LD (IX+07H),E

Store the overlay number (held in Register E) into the memory location pointed to by Special Index Register Pair IX+07H.
Note: IX+07H = the position in the DCB for the LOGICAL FILE NUMBER [the directory entry number]).

5945

CALL RDHIT
[4ABAH]

GOSUB to 4ABAH.
NOTE: 4ABAH is the SYS00/SYS routine to read the HIT sector into RAM.

5948

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

594B

RLC E

Let the overlay number = the overlay number * 2 via a rotate, since each extent is 2 bytes long.

594D

LD A,0E0H

Let Register A equal 0E0H (1110 0000) to indicate an overlay.

594F

ADD A,E

LET Register A = Register A + Register E so that Register A now holds the overlay number * 2 AND the overlay designation bytes.

5950
5951

LD L,A
LD H,43H

Let Register Pair HL = 43xx where xx is the overlay number * 2, which is the extent element for the applicable overlay.

5953

LD D,(HL)

Fetch the MSB of the extent element (held in the memory location pointed to by Register Pair HL) and store it into Register D. Note that file extents are in MSB/LSB order.

5954

INC HL

INCrement the value stored in Register Pair HL by 1.

5955

LD E,(HL)

Fetch the LSB of the extent element (held in the memory location pointed to by Register Pair HL) and store it into Register D.

5956

LD (6172H),DE

Store the extent element (the value held in Register Pair DE) into the FCB at memory location 6172H.

595A

LD A,0FFH

Let Register A equal 0FFH to flag a system file.

595C

LD (SYSFLG),A

Put a 0FFH (held in Register A) into memory location 599AH (i.e., the SYSTEM OVERLAY FLAG for the PATCH routine; NZ if system file being patched) to mark the file as a SYSTEM FILE and store it into Register A.

595F

POP HL

Put the pointer to the COMMAND LINE back into Register Pair HL.

5960

JP PAT0
[5727H]

JUMP to 5727H to continue the routine.

5963H – Patch File routine to update a system overlay file. The flags were preserved to the stack before this routine was called and are retrieved right after.

“CLOSYS”
5963

LD HL,(616CH)

Fetch “next” sector/record number from memory location 616CH and store it into Register Pair HL.

5966

DEC HL

Back up 1 record/sector by DECrementing the value stored in Register Pair HL by 1.

5967

LD (616CH),HL

Store the new “next” sector (held in Register Pair HL) into memory location 616CH.

596A

LD IX,S9DCB1

Let Special Index Register Pair IX equal 6162H which is the beginning of the SOURCE FILE DCB.

596E

CALL GETPDA
[49D4H]

Find the track/sector number of the “next sector” via a GOSUB to 49D4H.

5971

LD HL,BUFER1

Let Register Pair HL equal 6300H to point to the beginning of the READ FILE buffer.

5974

CALL 45F7H
[45F7H]

Write the sector at the “next” sector location via a GOSUB to 45F7H.

5977

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

597A

RET

RETurn to the caller.

597BH – Evaluate the overlay number a/k/a Convert a Decimal String into a Binary Value.

“HEXGET”
597B
597C

LD B,H
LD C,L

Let BC = HL (i.e., the pointer to the COMMAND LINE).

597D

LD HL,0000H

Let Register Pair HL equal 0000H for upcoming math.

“HEXGE1”
5980

LD A,(BC)

Fetch the next character (which is hopefully a digit) on the command line (held in the memory location pointed to by Register Pair BC) and store it into Register A.

5981

SUB 30H

5983

JR C,HEXGE2
[5996H]

If the C FLAG (Carry) has been set then the number fetched is below “0”, which is bad, so JUMP to 5996H.

5985

CP 0AH

Compare the value held in Register A against 0AH (Decimal: 10). Results:

If Register A equals 10, the Z FLAG is set.
If A < 10, the CARRY FLAG will be set.
if A >= 10, the NO CARRY FLAG will be set.

5987

JR NC,HEXGE2
[5996H]

If the NC FLAG (No Carry) has been set then the character is too high, which is bad, so JUMP to 5996H.

5989

INC BC

Point to the next character on the COMMAND LINE by INCrementing the value stored in Register Pair BC by 1.

598A
598B

LD D,H
LD E,L

Let DE = the current math value of the number (held in Register Pair HL).

598C
598D
598E
598F

ADD HL,HL
ADD HL,HL
ADD HL,HL
ADD HL,HL

LET Register Pair HL = Register Pair HL * 10 to move the value previously held in HL into the tens digit position.

5990
5991

LD E,A
LD D,00H

Let Register Pair DE = 00nn where nn is the value of the next digit in binary.

5993

ADD HL,DE

LET Register Pair HL = original number but in the 10’s place (held in Register Pair HL) + other character in the 1’s place (held in Register DE).

5994

JR HEXGE1
[5980H]

JUMP to 5980H to keep processing (and shifting nn to nn_).

5996H – Continuation of the above evaluation routine when the number found is less than 0 or more than 9.

“HEXGE2”
5996

EX DE,HL

EXchange the value stored in Register Pair HL (i.e., the converted number) with the value stored in Register Pair DE (irrelevant).

5997
5998

LD H,B
LD L,C

Let HL = BC (i.e., the pointer to the COMMAND LINE).

5999

RET

RETurn to the caller.

599AH – MESSAGE and STORAGE AREA.

“SYSFLG”
599A

DEFB 00H

Storage location for the System Overlay Flag. If NZ then the user wants to patch a SYSTEM OVERLAY file.

599BH – General Disk Routine. Open the disk file and preserve the LRL.

“OPENIT”
599B

CALL GETDCB
[59ADH]

Set up for FILE I/O via a GOSUB to 59ADH to set up for FILL SECTOR I/O and sets up registers B, DE, and HL.

599E

CALL 4424H
[4424H]

GOSUB to 4424H.
NOTE: 4424H is the SYS00/SYS routine to OPEN A DISK FILE for use. This RST 28H’s with a value of 92H so as to call ROUTINE 1 in OVERLAY 3.

59A1

PUSH AF

Save the contents of Register Pair AF (i.e., any error status from the OPEN) to the top of the stack.

59A2

LD A,(616BH)

Fetch the value held in memory location 616BH (i.e., the record length) and store it into Register A.

59A5

LD (LRLCHG),A

Store the value held in Register A into memory location 53A4H which is in the middle of a LD B,xx OPCODE.

59A8

LD (LRLCH1),A

Store the value held in Register A into memory location 54E0H.

59AB

POP AF

Restore the error status (held at the top of the STACK) into Register Pair AF, and then remove the entry from the stack.

59AC

RET

RETurn to the caller.

59ADH – General Disk Routine. Set up for full sector FILE I/O.

“GETDCB”
59AD

LD B,00H

Let Register B equal 00H to indicate FULL SECTOR FILE I/O / LRL of 256 bytes.

“GETDC1”
59AF

LD DE,S9DCB1

Let Register Pair DE equal 6162H which is the beginning of the SOURCE FILE DCB.

59B2

LD HL,BUFER1

Let Register Pair HL equal 6300H to point to the beginning of the READ FILE buffer.

59B5

RET

RETurn to the caller.

59B6H – General Disk Routine. Set up for full sector FILE I/O and Create A FiLE.

“INITIT”
59B6

CALL GETDCB
[59ADH]

GOSUB to GOSUB to 59ADH to set up for FILL SECTOR I/O and sets up registers B, DE, and HL.

59B9

JP 4420H
[4420H]

JUMP to 4420H.
NOTE: 4420H is the SYS00/SYS routine to INITIALIZE A FILE (i.e., CREATE or OPEN). This RST 28H’s with a value of A2H so as to call ROUTINE 2 in OVERLAY 2. Register HL needs to point to a RAM BUFFER for the DCB’s.

59BCH – General Disk Routine. Set Register Pair DE to point to the SOURCE FILE DCB, check the syntax of the associated Filespec, and RETurn.

“GETSYN”
59BC

LD DE,S9DCB1

Let Register Pair DE equal 6162H which is the beginning of the SOURCE FILE DCB.

59BF

JP 441CH
[441CH]

JUMP to 441CH.
NOTE: 441CH is the SYS00/SYS routine to CHECK THE SYNTAX OF A FILESPEC before for use. This RST 28H’s with a value of C1H so as to call ROUTINE 4 in OVERLAY 1.

59C2H – Patch Error Routine. Display a STRING NOT FOUND message and ABORT.

“PATERR”
59C2

LD HL,NOFID1

Let Register Pair HL equal 59D3H to point to the message “STRING NOT FOUND“.

59C5

JP 021BH
[021BH]

59C8H – MESSAGE and STORAGE AREA for the PATCH command.

“CHGMAD”
59C8

DEFM →

“‘PATCH MADE’ + 0DH“.

“NOFID1”
59D3

DEFM →

“‘STRING NOT FOUND’ + 0DH“.

“NOFIND”
59E4

DEFM →

“‘CAN’T FIND SPECIFIED ADDRESS’ + 0DH“.

“NOCHAG”
5A01

DEFM →

“‘NO CHANGE REQUIRED’ + 0DH“.

5A14H – “RELO” Routine. This routine ONLY updates t he LOAD FILE FORMAT ADDRESS, it does not “renum” the file.

“RELO”
5A14

LD DE,S9DCB

Let Register Pair DE equal 6130H, which is a pointer to the FILE CONTROL BLOCK.

5A17

CALL 441CH
[441CH]

GOSUB to 441CH.
NOTE: 441CH is the SYS00/SYS routine to CHECK THE SYNTAX OF A FILESPEC before for use. This RST 28H’s with a value of C1H so as to call ROUTINE 4 in OVERLAY 1.

5A1A

JP NZ,ERR3
[521DH]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to JUMP to 521DH.

5A1D

LD DE,RLTABL

Let Register Pair DE equal 5B12H, which is a pointer to the table to be parsed.

5A20

CALL 4454H
[4454H]

GOSUB to 4454H.
NOTE: 4454H is the DOS PARAMETER STRING PARSE routine. It decodes DOS LIBRARY parameters.

5A23

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5A26

LD HL,(RLADD)

Let Register Pair HL equal the relocation address, which is a value placed into 5A27H elsewhere in this overlay.

5A29

PUSH HL

Save the relocation address (held in Register Pair HL) to the top of the stack.

5A2A

LD HL,BUFER1

Let Register Pair HL equal 6300H to point to the beginning of the READ FILE buffer.

5A2D

LD DE,S9DCB

Let Register Pair DE equal 6130H, which is a pointer to the FILE CONTROL BLOCK.

5A30

LD B,00H

Let Register B equal 00H for a LRL of 256 bytes.

5A32

CALL 4424H
[4424H]

GOSUB to 4424H.
NOTE: 4424H is the SYS00/SYS routine to OPEN A DISK FILE for use. This RST 28H’s with a value of 92H so as to call ROUTINE 1 in OVERLAY 3.

5A35

JP NZ,EROR
[5B04H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 5B04H.

“LOOP2”
5A38

CALL ZREAD
[5AFBH]

Read a byte via a GOSUB to 5AFBH.

5A3B

PUSH AF

Save the byte (held in Register Pair AF) to the top of the stack.

5A3C

CALL ZREAD
[5AFBH]

Read a byte (which should be the number of bytes) via a GOSUB to 5AFBH.

5A3F

LD B,A

Copy the byte which was just read (held in Register A) into Register B, which will inform a DJNZ loop if the STALL routine is called because we hit a COMMENT FIELD.

5A40

POP AF

Put the first byte read (held at the top of the STACK) into Register Pair AF, and then remove the entry from the stack.

5A41

CP 05H

See if the first byte read was a COMMENT BYTE (i.e., 05H) by comparing the value held in Register A against 05H. Results: If Register A equals 05H, the Z FLAG is set; otherwise the NZ FLAG is set.

5A43

JP Z,STALL
[5AF3H]

If we have a comment byte, then the Z FLAG (Zero) will have been set, JUMP to 5AF3H to skip past B number bytes in the COMMENT BLOCK.

5A46

CP 01H

See if the first byte read was a CODE BLOCK (i.e., 01H) by comparing the value held in Register A against 01H. Results: If Register A equals 01H, the Z FLAG is set; otherwise the NZ FLAG is set.

5A48

JR Z,LOOP0
[5A4FH]

If we have a CODE BLOCK, then the Z FLAG (Zero) will have been set, JUMP to 5A4FH.

“LFERR”
5A4A

LD A,22H

If we haven’t jumped away, then we have an invalid block. Let Register A equal 22H to indicate an INVALID FILE FORMAT error.

5A4C

JP EROR
[5B04H]

Exit via a JUMP to 5B04H.

5A4FH – Part of the RELO command. Jumped here if the character indicated a CODE BLOCK.

“LOOP0”
5A4F

CALL ZREAD
[5AFBH]

Read a byte, which is the LSB of the address, via a GOSUB to 5AFBH.

5A52

LD L,A

Copy the LSB of the address (held in Register A) into Register L.

5A53

CALL ZREAD
[5AFBH]

Read a byte, which is the MSB of the address, via a GOSUB to 5AFBH.

5A56

LD H,A

Copy the MSB of the address (held in Register A) into Register L.

5A57

EX DE,HL

EXchange the value stored in Register Pair HL (the address just read) with the value stored in Register Pair DE (irrelevant).

5A58

POP HL

Restore the relocation address (held at the top of the STACK) into Register Pair HL, and then remove the entry from the stack.

5A59

PUSH HL

Save the relocation address (held in Register Pair HL) to the top of the stack.

5A5A

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5A5B

SBC HL,DE

Get the difference between the address in the code block and the requested address via a subtracts with carry which subtracts the value stored in Register Pair DE and the carry flag from the value stored in Register Pair HL.

5A5D

LD (5B1BH),HL

The result of that subtraction is in HL and is the offset. Store the offset (held in Register Pair HL) into memory location 5B1BH.

5A60

LD IY,BUFER2

Let Special Index Register Pair IY equal 6400H which will act as a buffer.

5A64

POP HL

Restore the relocation address (held at the top of the STACK) into Register Pair HL, and then remove the entry from the stack.

“LOOP3”
5A65

LD (IY+00H),01H

Store a CODE BLOCK indicator (i.e., 01H) into the memory location pointed to by Special Index Register Pair IY+00H.

5A69

INC IY

INCrement the value stored in Special Index Register IY by 1.

5A6B

LD (IY+00H),B

Store the character count (held in in Register B) into the memory location pointed to by Special Index Register Pair IY+00H.

5A6E

INC IY

INCrement the value stored in Special Index Register IY by 1.

5A70

LD (IY+00H),L

Store the LSB of the address (held in Register L) into the memory location pointed to by Special Index Register Pair IY+00H.

5A73

INC IY

INCrement the value stored in Special Index Register IY by 1.

5A75

LD (IY+00H),H

Store the MSB of the address (held in Register L) into the memory location pointed to by Special Index Register Pair IY+00H.

5A78
5A79

DEC B
DEC B

DECrement the value stored in Register B by 2 for the address.

5A7A

INC IY

INCrement the value stored in Special Index Register IY by 1.

“LOOP4”
5A7C

LD DE,S9DCB

Let Register Pair DE equal 6130H, which is a pointer to the FILE CONTROL BLOCK.

5A7F

CALL ZREAD
[5AFBH]

Read a byte via a GOSUB to 5AFBH.

5A82

LD (IY+00H),A

Store the value held in Register A into the memory location pointed to by Special Index Register Pair IY+00H.

5A85

INC IY

INCrement the value stored in Special Index Register IY by 1.

5A87

DJNZ LOOP4
[5A7CH]

LOOP back to 5A7CH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5A89

CALL ZREAD
[5AFBH]

Read a byte, which will be the LOAD FILE HEADER, via a GOSUB to 5AFBH.

5A8C

CP 02H

Check to see if we are at the end of the record via receipt of an 02H by comparing the value held in Register A against 02H. Results: If Register A equals 02H, the Z FLAG is set; otherwise the NZ FLAG is set.

5A8E

JR Z,LOOP7
[5AA9H]

If we fetched an 02H byte, then we are at the end of the record and the Z FLAG (Zero) will have set, JUMP to 5AA9H to exit.

5A90

CP 01H

See if the byte read was a CODE BLOCK (i.e., 01H) by comparing the value held in Register A against 01H. Results: If Register A equals 01H, the Z FLAG is set; otherwise the NZ FLAG is set.

5A92

JP NZ,LFERR
[5A4AH]

If we did NOT fetch an 01H, then we have a problem and the NZ FLAG (Not Zero) will have been set, JUMP to 5A4AH.

5A95

CALL ZREAD
[5AFBH]

Read a byte (the character count) via a GOSUB to 5AFBH.

5A98

LD B,A

Copy the character count (held in Register A) into Register B.

5A99

CALL ZREAD
[5AFBH]

Read a byte, which is the LSB of the address, via a GOSUB to 5AFBH.

5A9C

LD L,A

Copy the LSB of the address (held in Register A) into Register L.

5A9D

CALL ZREAD
[5AFBH]

Read a byte, which is the MSB of the address, via a GOSUB to 5AFBH.

5AA0

LD H,A

Copy the MSB of the address (held in Register A) into Register H.

5AA1

LD DE,(SAVE)

Fetch the offset value (held in memory location 5B1BH) and store it into Register Pair DE.

5AA5

ADD HL,DE

Add the offset to the load address by LETing Register Pair HL = Register Pair HL (load address) + Register DE (offset to the requested load address).

5AA6

JP LOOP3
[5A65H]

Continue via a JUMP BACK to 5A65H.

5AA9H – Part of the RELO command. Jumped here if loop to read the characters in the prior routine hit an 02H to indicate END OF RECORD.

“LOOP7”
5AA9

LD (IY+00H),A

Store the value held in Register A (i.e., an 02H) into the memory location pointed to by Special Index Register Pair IY+00H.

5AAC

INC IY

INCrement the value stored in Special Index Register IY by 1.

5AAE

CALL ZREAD
[5AFBH]

Read a byte (which will be an 02H) via a GOSUB to 5AFBH.

5AB1

CALL ZREAD
[5AFBH]

Read a byte (the LSB of the entry address) via a GOSUB to 5AFBH.

5AB4

LD (IY+00H),02H

Store the lneght of the data which follows (i.e., 2 bytes) into the memory location pointed to by Special Index Register Pair IY+00H.

5AB8

INC IY

INCrement the value stored in Special Index Register IY by 1.

5ABA

LD (IY+00H),A

Store the LSB of the address (held in Register A) into the memory location pointed to by Special Index Register Pair IY+00H.

5ABD

INC IY

INCrement the value stored in Special Index Register IY by 1.

5ABF

CALL ZREAD
[5AFBH]

Read a byte (the MSB of the entry address) via a GOSUB to 5AFBH.

5AC2

LD (IY+00H),A

Store the MSB of the address (held in Register A) into the memory location pointed to by Special Index Register Pair IY+00H.

5AC5

INC IY

INCrement the value stored in Special Index Register IY by 1.

5AC7

LD (SAVE1),IY

Store the value held in Special Index Register Pair IY (i.e., the end pointer) into memory location 5B1DH.

5ACB

LD DE,S9DCB

Let Register Pair DE equal 6130H, which is a pointer to the FILE CONTROL BLOCK.

5ACE

CALL 443FH
[443FH]

GOSUB to 443FH.
NOTE: 443FH is the SYS00/SYS vector for ‘REWIND’, which will rewind the open file.

5AD1

JP NZ,EROR
[5B04H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to JUMP to 5B04H.

5AD4

LD HL,(SAVE1)

Fetch the end pointer (held in memory location 5B1DH) and store it into Register Pair HL.

5AD7

LD DE,BUFER2

Let Register Pair DE equal 6400H which is a BUFFER in RAM for DATA.

5ADA

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5ADB

SBC HL,DE

Determine the applicable number of bytes by subtracting the value stored in Register Pair DE (the buffer starting address) and the carry flag from the value stored in Register Pair HL (the end pointer).

5ADD
5ADE

LD B,H
LD C,L

Let Register Pair BC = the number of applicable bytes (held in Register Pair HL).

5ADF

EX DE,HL

EXchange the buffer address (stored in Register Pair HL) with the number of bytes (stored in Register Pair DE).

5AE0

LD DE,S9DCB

Let Register Pair DE equal 6130H, which is a pointer to the FILE CONTROL BLOCK.

“LOOP8”
5AE3

LD A,(HL)

Fetch the a character held in the memory location pointed to by Register Pair HL and store it into Register A.

5AE4

CALL ZWRITE
[5B07H]

Write that character out via a GOSUB to 5B07H.

5AE7

INC HL

INCrement the buffer pointer (stored in Register Pair HL) by 1.

5AE8

DEC BC

DECrement the byte counter (stored in Register Pair BC) by 1.

5AE9
5AE9

LD A,B
OR C

5AEB

JR NZ,LOOP8
[5AE3H]

If the byte counter did NOT hit zero, then the NZ FLAG (Not Zero) will have been set, so LOOP BACK to 5AE3H.

5AED

CALL 4428H
[4428H]

GOSUB to 4428H to CLOSE the file
NOTE: 4428H is the SYS00/SYS routine to CLOSE A DISK FILE. This RST 28H’s with a value of 93H so as to call ROUTINE 1 in OVERLAY 3.

5AF0

JP 402DH
[402DH]

Return to DOS READY via a JUMP to the SYS00/SYS vector at 402DH.

5AF3H – Continuation of RELO Command. Jumped here if we need to skip over all the bytes in a COMMENT block. Requires Register B to contain the number of bytes in the COMMENT BLOCK to be skipped.

“STALL”
5AF3

CALL ZREAD
[5AFBH]

Read a byte via a GOSUB to 5AFBH.

5AF6

DJNZ 5AF3H
[5AF3H]

LOOP back to 5AF3H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5AF8

JP LOOP2
[5A38H]

JUMP back into the applicable loop of the RELO routine – 5A38H.

5AFBH – Continuation of RELO Command. Thgis routine reads a byte and puts it into Register A.

“ZREAD”
5AFB

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

5AFC

LD DE,S9DCB

Let Register Pair DE equal 6130H, which is a pointer to the FILE CONTROL BLOCK.

5AFF

CALL 0013H
[0013H]

GOSUB to 0013H.
NOTE: 0013H is the Model III ROM routine to read a byte from an input device. Requires DE = starting address of DCB of device and on Exit Register A = byte received from device, Z set if device ready. Uses AF.

5B02

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

5B03

RET Z

If the Z FLAG (Zero) has been set, RETurn to the caller.

5B04H – Continuation of the RELO Command. Exit to the error handler.

“EROR”
5B04

JP 4409H
[4409H]

JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

5B07H – Continuation of the RELO Command. Write a byte out.

“ZWRITE”
5B07

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

5B08

LD DE,S9DCB

Let Register Pair DE equal 6130H, which is a pointer to the FILE CONTROL BLOCK.

5B0B

CALL 001BH
[001BH]

GOSUB to 001BH.
NOTE: 001BH is the Model III ROM routine to write a byte to an output device. Requires Register A to contain the byte to output and Register Pair DE to be the starting address of DCB of device. On exit, Z set if device ready. Uses AF.

5B0E

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

5B0F

RET Z

If the Z FLAG (Zero) has been set, RETurn to the caller.

5B10

JR EROR
[5B04H]

Exit to the exit handler via a JUMP to 5B04H.

5B12H – MESSAGE and STORAGE AREA for the RELO COMMAND.

“RLTABL”
5B12

DEFM ‘ADD ‘

DEFW RLADD

A 2 byte storage location to hold the relocation address

DEFB 00H

“SAVE”

DEFS 2

General storage location of 2 bytes.

“SAVE1”

DEFS 2

General storage location of 2 bytes.

5B1FH – Main Routine – “FORMS”.

“FORMS”
5B1F

LD BC,0000H

Let Register Pair BC equal 0000H for the next two instructions.

5B22

LD (CHAR),BC

Clear the PRINTER WIDTH flag by putting a 00H into memory location 5B44H.

5B26

LD (FLINE),BC

Clear the PAGE LENGTH flag by putting a 00H into memory location 5B51H.

5B2A

CALL SKIPSP
[5F8EH]

Get the next non-space COMMAND LINE character via a GOSUB to 5F8EH.

5B2D

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN, the Z FLAG is set; otherwise the NZ FLAG is set.

5B2F

JR NZ,5B36H
[5B36H]

If we did NOT get a CARRIAGE RETURN, then we got more than just the FORMS command alone as a command and the NZ FLAG (Not Zero) will have been set, JUMP to 5B36H.

5B31

LD A,0CH

Let Register A equal 0CH which is the FORM FEED.

5B33

JP 003BH
[003BH]

JUMP to 003BH.
NOTE: 003BH is the Model III ROM routine to write the byte held in Register A to the printer, including waiting for the printer to be available OR getting a BREAK. Uses Register Pair DE. Since this was JUMPED to instead of CALLed, the RET at the end of this ROM routine will then RETurn to the caller of this subroutine instead of returning to this place.

5B36H – Continuation of the “FORMS” Routine. Jumped here if we determined that we actually got parameters on the COMMAND LINE.

“FORMS1”
5B36

LD DE,FORCOM

Let Register Pair DE equal 5B5FH which is a pointer to the table of valid FORMS parameters.

5B39

CALL 4454H
[4454H]

GOSUB to 4454H.
NOTE: 4454H is the DOS PARAMETER STRING PARSE routine. It decodes DOS LIBRARY parameters.

5B3C

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

“FORMS2”
5B3F

LD IX,4025H

Let Special Index Register Pair IX equal 4025H, which is the PRINTER DCB.

5B43

LD HL,(CHAR)

Let Register Pair HL equal the LINE WIDTH, placed elsewhere in this overlay.

5B46

CALL CONVHX
[6086H]

Convert the character held in Register Pair HL into hexadecimal via a GOSUB to 6086H.

5B49
5B49

LD A,H
OR L

Since the Z-80 cannot test Register Pair HL against zero, the common trick is to set Register A to equal to Register H, and then OR A against Register L. Only if both Register H and Register L were zero can the Z FLAG be set.

5B4B

JR Z,FORMS3
[5B50H]

If the user didn’t select anything (and the result of the hexidecimal conversion was a 00) the Z FLAG (Zero) will have been set; JUMP to 5B50H to try lines per page.

5B4D

LD (IX+06H),L

Store the user count (held in Register L) into the memory location pointed to by Special Index Register Pair IX+06H.
Note: IX+06H = the position in the PRINTER DCB for LINE WIDTH.

“FORMS3”
5B50

LD HL,(FLINE)

Let Register Pair HL equal the PAGE LENGTH, placed elsewhere in this overlay.

5B53

CALL CONVHX
[6086H]

Convert the character held in Register Pair HL into hexadecimal via a GOSUB to 6086H.

5B56
5B56

LD A,H
OR L

5B58

RET Z

If there is no value held in HL then there is no line length to set, so exit via a RETurn to the caller.

5B59

INC L

INCrement the value stored in Register L by 1, to see if THAT produces a zero (which means it was FF, or INDEFINITE).

5B5A

RET Z

If the Z FLAG (Zero) is STILL set, exit via a RETurn to the caller.

5B5B

LD (IX+03H),L

Store the new lines per page value (held in Register L) into the memory location pointed to by Special Index Register Pair IX+03H.
Note: IX+03H = the position in the PRINTER DCB for LINES PER PAGE.

5B5E

RET

RETurn to the caller.

5B5FH – Continuation of the “FORMS” Routine. MESSAGE and BYTE STORAGE.

“FORCOM”
5B5F

DEFM ‘WIDTH ‘

DEFW CHAR

DEFM ‘LINES ‘

DEFW FLINE

DEFB 00H

End of Parameter List Terminator

5B70H – General Subroutine. Compare DE and HL Strings.

“COMPAR”
5B70

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

5B71

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

5B72

PUSH HL

Save the contents of Register Pair HL to the top of the stack.

“COMPA1”
5B73

LD A,(DE)

Fetch the value held in the memory location pointed to by Register Pair DE and store it into Register A.

5B74

CP (HL)

Compare the value held in Register A against the value held in the memory location pointed to by Register Pair HL. Results: If Register A equals the value held in Register HL, the Z FLAG is set; otherwise the NZ FLAG is set.

5B75

JR NZ,COMPA2
[5B7CH]

If there is no match, then the NZ FLAG (Not Zero) will have been set, JUMP to 5B7CH.

5B77

LDI

Move to the 2nd character of both HL and DE via LDI command; which copies BC number of characters from (HL) to (DE), dropping BC each time. When BC hits 0, the PE flag is reset.

5B79

JP PE,COMPA1
[5B73H]

LOOP BACK to 5B73H until finished.

“COMPA2”
5B7C

POP HL

Put the value held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

5B7D

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

5B7E

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

5B7F

RET

RETurn to the caller.

5B80H – Display “MESSAGE” + ” = “. HL must point to the message

“PDATA”
5B80

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

5B83

LD HL,S9EQU

Let Register Pair HL equal 5B96H to point to the message ” = “.

5B86

JP 021BH
[021BH]

5B89H – Display “MESSAGE” + “, “. HL must point to the message

“PDATA1”
5B89

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

“PDATA2”
5B8C

LD A,PCHANG

Let Register A equal ,. Note, this can be changed to a different character if the routine is to display with a space instead of a comma.

5B8E

CALL 0033H
[0033H]

GOSUB to 0033H.
NOTE: 0033H is the Model III ROM character print routine; displays the character held in Register A at the current cursor position.

5B91

LD A,20H

Let Register A equal SPACE.

5B93

JP 0033H
[0033H]

5B96H – MESSAGE AND STORAGE AREA.

“S9EQU”5B96

DEFM ” = ” +03H

5B9AH – NEW “ROUTE” COMMAND. This was deprecated, and the below 2 instructions just throw an error.

“ROUTE”
5B9A

LD A,1FH

Let Register A equal 1FH to point to the error PROGRAM NOT FOUND.

5B9C

JP 4409H
[4409H]

JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

5B9AH – OLD “ROUTE” COMMAND. Before the ROUTE command was deprecated, the code was …

5B9A

LD A,(442FH)

Let Register A equal the contents of the memory location 442FH, which was the ROUTE/DUAL Flag.

5B9C

CP 80H

Check to see if the ROUTE/DUAL Flag at 442FH was 80H (meaning that ROUTE was active).

5B9F

JR Z,ROUTIT
[5BA5H]

If the ROUTE command was already active, then the Z FLAG (Zero) will have been set, so JUMP to 5BA5H.

5BA1

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5BA2

JP NZ,NOROTE
[5C3AH]

If the DUAL command was already active, then the NZ FLAG (Zero) will have been set, so JUMP to 5C3AH.

If we are here then neither the ROUTE nor DUAL was set, so we need to actually process the command.

“ROUTIT”
5BA5

CALL SKIPSP
[5F8EH]

Get the next non-space COMMAND LINE character via a GOSUB to 5F8EH.

5BA8

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE). Results:

If Register A equals SPACE, the Z FLAG is set.
If A < SPACE, the CARRY FLAG will be set.
if A >= SPACE, the NO CARRY FLAG will be set.

5BAA

JP C,0069H
[0069H]

If the COMMAND LINE character is < SPACE, meaning we got no valid parameter when the command was called, the C FLAG (Carry) will have been set, JUMP to 0069H to initialize the drivers.

5BAD

CP 28H

Compare the value held in Register A against 28H (ASCII: (). Results: If Register A equals (, the Z FLAG is set; otherwise the NZ FLAG is set.

5BAF

JP NZ,ERR3
[521DH]

If we are here, then we need a valid command line, which would necessitate that the next character is a (. If we did not get the (, then the NZ FLAG (Not Zero) will have been set, JUMP to 521DH to exit with an error.

5BB2

INC HL

Point to the next character on the command line, following the (, by INCrementing the value stored in Register Pair HL by 1.

“REROT”
5BB3

LD DE,S9SRC1

Let Register Pair DE equal 5C5DH, which points to the word “SOURCE”.

5BB6

LD A,(DE)

Fetch the parameter length (held in the memory location pointed to by Register Pair DE) and store it into Register A.

5BB7
5BB8

LD C,A
LD B,00H

Let Register Pair BC = the parameter length.

5BBA

INC DE

INCrement the value stored in Register Pair DE by 1 to now point to the word “SOURCE”.

5BBB

CALL COMPAR
[5B70H]

Compare HL and DE to see if they match via a GOSUB to 5B70H.

5BBE

JR NZ,ROUTE5
[5BF4H]

If they don’t match, then we didn’t get “SOURCE”. Maybe we got “DEST” so JUMP to 5BF4H.

5BC0

ADD HL,BC

Point Register Pair HL to the next parameter by advancing HL by BC bytes so now the COMMAND LINE Pointer points to the “=”.

5BC1

CALL GETTOK
[5C10H]

Get the device name from the COMMAND LINE via a GOSUB to 5C10H.

5BC4

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error (which would be that the parameter didn’t match any valid device), so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5BC7

PUSH HL

Save the position on the COMMAND LINE (held in Register Pair HL) to the top of the stack.

5BC8

EX DE,HL

EXchange the value stored in Register Pair HL (the position on the COMMAND LINE) with the value stored in Register Pair DE (the SOURCE name).

5BC9

LD DE,4222H

Let Register Pair DE equal 4222H which points to the ROUTE DCB for the DESTINATION name.

“ROUTE1”
5BCC

LD BC,0002H

Let Register Pair BC equal 0002H since there are 2 characters in a valid ROUTE source/destination.

5BCF

LDIR

5BD1

POP HL

Restore the position on the COMMAND LINE from the top of the stack into Register Pair HL, and then remove the entry from the stack.

5BD2
5BD3

INC HL
INC HL

Skip the 2 character device name on the COMMAND LINE by INCrementing the value stored in Register Pair HL by 2.

“ROUTE2”
5BD4

LD A,(HL)

Fetch the next character on the COMMAND LINE from the memory location pointed to by Register Pair HL and store it into Register A.

5BD5

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE). Results: If Register A equals SPACE, the Z FLAG is set; otherwise the NZ FLAG is set.

5BD7

JR Z,ROUTE4
[5BF1H]

If we got a SPACE then we need to keep looking for the next valid character on the COMMAND LINE and the Z FLAG (Zero) will have been set, JUMP to 5BF1H to point the next character on the COMMAND LINE and then JUMP to 5BD4H.

5BD9

CP ‘,’

Compare the value held in Register A against ,. Results: If Register A equals ,, the Z FLAG is set; otherwise the NZ FLAG is set.

5BDB

JR Z,ROUTE4
[5BF1H]

If we got a , then we need to keep looking for the next valid character on the COMMAND LINE and the Z FLAG (Zero) will have been set, JUMP to 5BF1H to point the next character on the COMMAND LINE and then JUMP to 5BD4H.

5BDD

CP 29H

Compare the value held in Register A against 29H (ASCII: )). Results: If Register A equals ), the Z FLAG is set; otherwise the NZ FLAG is set.

5BDF

JR Z,ROUTE3
[5BE5H]

If we got a ) then we are at the end of the command and the Z FLAG (Zero) will have been set, JUMP to 5BE5H.

5BE1

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN, the Z FLAG is set; otherwise the NZ FLAG is set.

5BE3

JR NZ,REROT
[5BB3H]

If the next character was NOT a CARRIAGE RETURN then we have more COMMAND LINE to search. JUMP to 5BB3H.

“ROUTE3”
5BE5

LD A,80H

Let Register A equal 80H, which is the ROUTE/DUAL FLAG for “ROUTE ACTIVE”.

5BE7

LD (442FH),A

Store the value held in Register A into memory location 442FH, which is the ROUTE/DUAL FLAG.

5BEA

CALL 006CH
[006CH]

GOSUB to 006CH to route the devices.

5BED

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5BF0

RET

RETurn to the caller.

5BF1H – ROUTINE inside the ROUTE COMMAND. Move the pointer to the current character on the COMMAND LINE by 1 and then JUMP to 5BD4H.

“ROUTE4”
5BF1

INC HL

Point to the next character on the command line by INCrementing the value stored in Register Pair HL by 1.

5BF2

JR ROUTE2
[5BD4H]

JUMP BACK to 5BD4H.

5BF4H – ROUTINE inside the ROUTE COMMAND. Process the DESTINATION.

“ROUTE5”
5BF4

LD DE,S9DES1

Let Register Pair DE equal 5C64H, which points to the word “DESTIN”.

5BF7

LD A,(DE)

Fetch the parameter length (held in the memory location pointed to by Register Pair DE) and store it into Register A.

5BF8
5BF9

LD C,A
LD B,00H

Let Register Pair BC = the parameter length.

5BFB

INC DE

INCrement the value stored in Register Pair DE by 1 to now point to the word “DESTIN”.

5BFC

CALL COMPAR
[5B70H]

Compare HL and DE to see if they match via a GOSUB to 5B70H.

5BFF

JP NZ,ERR2
[5219H]

If they don’t match, then we didn’t get the correct parameter and the NZ FLAG (Not Zero) will have been set, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5C02

ADD HL,BC

Point Register Pair HL to the next COMMAND LINE character after DESTIN by advancing HL by BC bytes.

5C03

CALL GETTOK
[5C10H]

Get the device name from the COMMAND LINE via a GOSUB to 5C10H.

5C06

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5C09

PUSH HL

Save the position on the COMMAND LINE (held in Register Pair HL) to the top of the stack.

5C0A

EX DE,HL

EXchange the value stored in Register Pair HL (the position on the COMMAND LINE) with the value stored in Register Pair DE (the DESTINATION name).

5C0B

LD DE,4220H

Let Register Pair DE equal 4220H which points to the ROUTE DCB for the DESTINATION name.

5C0E

JR ROUTE1
[5BCCH]

JUMP into the prior routine to move the bytes and then keep polling the COMMAND LINE.

5C10H – Continuation of the ROUTE routine; process the actual source/destination device code.

“GETTOK”
5C10

LD A,(HL)

Fetch the next character from the command line (held in the memory location pointed to by Register Pair HL) and store it into Register A.

5C11

CP 3DH

Compare the value held in Register A against 3DH (ASCII: =).

5C13

RET NZ

If the next character was NOT a (ASCII: =), the NZ FLAG (Not Zero) will have been set, RETurn to the caller.

5C14

INC HL

Point to the next character on the command line, following the =, by INCrementing the value stored in Register Pair HL by 1.

5C15

LD DE,DO1

Let Register Pair DE equal 5C6BH, which points to the word “DO” (meaning the DISPLAY).

5C18

LD BC,0002H

Let Register Pair BC equal 0002H.

5C1B

CALL COMPAR
[5B70H]

Compare HL and DE to see if they match via a GOSUB to 5B70H.

5C1E

RET Z

If command line pointed to “DO” then the Z FLAG (Zero) will have been set, RETurn to the caller.

5C1F

LD DE,KB1

Let Register Pair DE equal 5C6DH, which points to the word “KB” (meaning the KEYBOARD).

5C22

CALL COMPAR
[5B70H]

Compare HL and DE to see if they match via a GOSUB to 5B70H.

5C25

RET Z

If command line pointed to “KB” then the Z FLAG (Zero) will have been set, RETurn to the caller.

5C26

LD DE,PR1

Let Register Pair DE equal 5C6FH, which points to the word “PR” (meaning the PRINTER).

5C29

CALL COMPAR
[5B70H]

Compare HL and DE to see if they match via a GOSUB to 5B70H.

5C2C

RET Z

If command line pointed to “PR” then the Z FLAG (Zero) will have been set, RETurn to the caller.

5C2D

LD DE,RO1

Let Register Pair DE equal 5C71H, which points to the word “RO” (meaning the RS-232 OUT).

5C30

CALL COMPAR
[5B70H]

Compare HL and DE to see if they match via a GOSUB to 5B70H.

5C33

RET Z

If command line pointed to “RO” then the Z FLAG (Zero) will have been set, RETurn to the caller.

5C34

LD DE,RI1

Let Register Pair DE equal 5C73H, which points to the word “RI” (meaning the RS-232 IN).

5C37

JP 5B70H
[5B70H]

Compare HL and DE to see if they match via a JUMP (not GOSUB) to 5B70H.

5C3AH – Abort out of the ROUTE command via a “CAN’T ROUTE” Error.

“NOROTE”
5C3A

LD HL,RTMSG

Let Register Pair HL equal 5C40H, which points to the message “CAN’T ROUTE”.

5C3D

JP 021BH
[021BH]

5C40H – MESSAGE and BYTE STORAGE AREA for the ROUTE COMMEND.

“RTMSG”
5C40

DEFM →

“CAN’T ROUTE WHILE DUAL IS ON“.

“S9SRC1”
5C5D

DEFB 06H

Byte count for the word “SOURCE”.

5C5E

DEFM “SOURCE”

“S9DES1”
5C64

DEFB 06H

Byte count for the word “DESTIN”.

5C65

DEFM “DESTIN”

“DO1”
5C6B

DEFM “DO”

“KB1”
5C6D

DEFM “KB”

“PR1”
5C6F

DEFM “PR”

“RO1”
5C71

DEFM “RO”

“RI1”
5C73

DEFM “RI”

5C75H – “SETCOM” Command – Configure the RS-232.

“SETCOM”
5C75

CALL SKIPSP
[5F8EH]

Get the next non-space COMMAND LINE character via a GOSUB to 5F8EH.

5C78

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE). Results:

If Register A equals SPACE, the Z FLAG is set.
If A < SPACE, the CARRY FLAG will be set.
if A >= SPACE, the NO CARRY FLAG will be set.

5C7A

JP NC,SETCO1
[5D1FH]

If the character from the command line is >= SPACE, meaning we have an ALPHANUMERIC character, then the NC FLAG (No Carry) will have been set, JUMP to 5D1FH.

5C7D

LD A,(41F9H)

Fetch the value held in memory location 41F9H (which is where the RS-232 configuration is stored) and store it into Register A.

5C80

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5C81

JP Z,SETOFF
[5D09H]

If the RS-232 Configuration Byte is zero, then the RS-232 is disabled; JUMP to 5D09H.

5C84

LD HL,BAUDMG

Let Register Pair HL equal 5E9FH, which is the pointer to the “BAUD = ” message.

5C87

CALL PDATA
[5B80H]

GOSUB to 5B80H to display the “BAUD = ” message.

5C8A

LD A,(41F8H)

Fetch the value held in memory location 41F8H (which is where the RS-232 BAUD RATE is stored) and store it into Register A.

5C8D

AND 0FH

MASK the value of Register A against 0FH (0000 1111). This has the effect of leaving only bits 3, 2, 1, 0 active, which hold the RECEIVE BAUD RATE.

5C8F

ADD A,A

LET Register A = Register A * 2, because each entry in the table is 2 bytes.

5C90
5C91

LD C,A
LD B,00H

Let Register Pair BC = The doubled, masked, RS-232 Baud Rate (held in Register A).

5C93

LD HL,TABLE2

Let Register Pair HL equal 5E81H, which is the top of the BAUD RATE LOOKUP TABLE (which is a table of JUMP points, based on position, to the ASCII renditions of a BAUD Rate).

5C96

ADD HL,BC

Move HL down the BAUD RATE LOOKUP TABLE by the OFFSET held in Register Pair BC.

5C97

LD E,(HL)

Fetch the LSB of the location of the Baud Rate Text (held in the memory location pointed to by Register Pair HL) and store it into Register E.

5C98

INC HL

INCrement the value stored in Register Pair HL by 1 to as to point to the next byte of the BAUD RATE LOOKUP TABLE.

5C99

LD D,(HL)

Fetch the MSB of the location of the Baud Rate Text (held in the memory location pointed to by Register Pair HL) and store it into Register E.

5C9A

EX DE,HL

EXchange the value stored in Register Pair HL (currently pointing to the 2nd byte of the 2 byte address for the BAUD RATE LOOKUP TABLE) with the value stored in Register Pair DE (the address of the desired BAUD RATE text).

5C9B

CALL PDATA1
[5B89H]

Display the baud rate and a comma via a GOSUB to 5B89H.

5C9E

LD HL,UARTMG

Let Register Pair HL equal 5EA4H, which is a pointer to the message “WORD = “.

5CA1

CALL PDATA
[5B80H]

Display the message “WORD = ” via a GOSUB to 5B80H.

5CA4

LD A,(41F9H)

Fetch the value held in memory location 41F9H (which is where the RS-232 Configuration Byte is stored) and store it into Register A.

5CA7

AND 60H

MASK the value of Register A against 60H (0110 0000) leaving only bits 6 and 5 active.

5CA9
5CAA
5CAB

RLCA
RLCA
RLCA

Rotate the bits in A left (with Bit 7 going into Bit 0) three times so that the 2 bytes of the WORD code are in Bits 1 and 0.

5CAC

ADD A,A

LET Register A = Register A * 2, because each entry in the table is 2 bytes.

5CAD
5CAE

LD C,A
LD B,00H

Let Register Pair BC = The doubled, masked, RS-232 Word Length(held in Register A).

5CB0

LD HL,TABLE1

Let Register Pair HL equal 5E79H, which is the top of the WORD LENGTH LOOKUP TABLE (which is a table of JUMP points, based on position, to the ASCII renditions of the WORD LENGTH).

5CB3

ADD HL,BC

Let Register Pair HL = the top of the lookup table (Register Pair HL) + an offset (Register BC).

5CB4

LD E,(HL)

Fetch the LSB of the location of the WORD LENGTH LOOKUP TABLE (held in the memory location pointed to by Register Pair HL) and store it into Register E.

5CB5

INC HL

INCrement the value stored in Register Pair HL by 1 to as to point to the next byte of the WORD LENGTH LOOKUP TABLE.

5CB6

LD D,(HL)

Fetch the MSB of the location of the WORD LENGTH LOOKUP TABLE (held in the memory location pointed to by Register Pair HL) and store it into Register E.

5CB7

EX DE,HL

EXchange the value stored in Register Pair HL (currently pointing to the 2nd byte of the 2 byte address for the WORD LENGTH LOOKUP TABLE) with the value stored in Register Pair DE (the address of the desired WORD LENGTH text).

5CB8

CALL PDATA1
[5B89H]

Display the word length and a comma via a GOSUB to 5B89H.

5CBB

LD HL,STOPMG

Let Register Pair HL equal 5EA9H, which is a pointer to the message “STOP = “.

5CBE

CALL PDATA
[5B80H]

Display the message “STOP = ” via a GOSUB to 5B80H.

5CC1

LD A,(41F9H)

Fetch the value held in memory location 41F9H (which is where the RS-232 configuration is stored) and store it into Register A.

5CC4

BIT 4,A

Test Bit Number 4 (which is the STOP bit) of Register A. Z FLAG will be set if that bit is 0, and NZ FLAG will be set if that bit is 1.

5CC6

LD A,31H

Let Register A equal 31H (ASCII: 1).

5CC8

JR Z,5CCBH
[5CCBH]

If the Z FLAG (Zero) has been set, then there is ONE stop bit, so skip the next instrution (which sets up for a display of “2”) and JUMP to 5CCBH.

5CCA

INC A

INCrement the value stored in Register A by 1 to now be a 2.

“SETNO1”
5CCB

CALL 0033H
[0033H]

GOSUB to 0033H.
NOTE: 0033H is the Model III ROM character print routine; displays the character held in Register A at the current cursor position.

5CCE

CALL PDATA2
[5B8CH]

Display a “,” via a GOSUB to 5B8CH.

5CD1

LD HL,PARTMG

Let Register Pair HL equal 5EAEH, which is a pointer to the message “PARITY = “.

5CD4

CALL PDATA
[5B80H]

Display the message “PARITY = ” via a GOSUB to 5B80H.

5CD7

LD A,(41F9H)

Fetch the value held in memory location 41F9H (which is where the RS-232 Configuration Byte is stored) and store it into Register A.

5CDA

LD HL,5EB5H

Let Register Pair HL equal 5EB5H, which is a pointer to the message “NONE”.

5CDD

BIT 3,A

Test Bit Number 3 of Register A to determine the PARITY status. Z FLAG will be set if that bit is 0 (which will mean PARITY IS ON), and NZ FLAG will be set if that bit is 1 (which will mean PARITY IS OFF).

5CDF

JP NZ,S9NOT3
[5CECH]

If Parity is OFF then the NZ FLAG (Not Zero) will have been set. No need to determine ODD or EVEN so skip over all that via a JUMP to 5CECH.

“S9NOT2”
5CE2

LD HL,ODD

Let Register Pair HL equal 5EBAH, which is a pointer to the message “ODD”.

5CE5

BIT 7,A

Test Bit Number 7 of Register A to determine if the PARITY is odd or even. Z FLAG will be set if that bit is 0 (meaning ODD PARITY), and NZ FLAG will be set if that bit is 1 (meaning EVEN PARITY).

5CE7

JR Z,5CECH
[5CECH]

If Bit 7 was 0, then we have ODD PARITY and the Z FLAG (Zero) will have been set. No need to determine EVEN parity, so skip over that via a JUMP to 5CECH.

5CE9

LD HL,5EBEH

Let Register Pair HL equal 5EBEH, which is a pointer to the message “EVEN”.

“S9NOT3”
5CEC

CALL PDATA1
[5B89H]

Display the message pointed to by Register Pair HL (either NONE, ODD, or EVEN) and a “,” via a GOSUB to 5B89H.

5CEF

LD A,20H

Let Register A equal 20H (ASCII: SPACE).

5CF1

LD (5B8DH),A

Store the value held in Register A into memory location 5B8DH, which is where the “,” has been for all the prior calls.

5CF4

LD A,(41FAH)

Fetch the value held in memory location 41FAH (which is the RS-232 WAIT FLAG location) and store it into Register A. 0=Wait, 1=No Wait.

5CF7

LD HL,WAITS

Let Register Pair HL equal 5EC3H, which is a pointer to the message “WAIT”.

5CFA

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5CFB

JR NZ,S9NOT4
[5D00H]

If the byte means we have a WAIT then the NZ FLAG (Not Zero) will have been set, JUMP to 5D00H.

5CFD

LD HL,NWAITS

Let Register Pair HL equal 5EC8H, which is a pointer to the message “NO WAIT”.

“S9NOT4”
5D00

CALL PDATA1
[5B89H]

Display the WAIT STATUS, whatever it is, via a GOSUB to 5B89H.

5D03

LD HL,SMODE

Let Register Pair HL equal 5ED0H, which is a pointer to the message “MODE”.

5D06

JP PDATA1
[5B89H]

Display the message “MODE” and RETurn via a JUMP to 5B89H.

5D09H – SETCOM Routine – Turn the RS-232 Off.

“SETOFF”
5D09

XOR A

Set Register A to ZERO and clear all Flags.

5D0A

LD (41F8H),A

Zero out the BAUD RATE by storing the value held in Register A into memory location 41F8H (RS-232 Baud Rate).

5D0D

LD (41F9H),A

Zero out the UART CONFIGURATION by storing the value held in Register A into memory location 41F9H (RS-232 Configuration Byte).

5D10

DEC A

DECrement the value stored in Register A by 1 to now be FFH.

5D11

LD (41FAH),A

Enbale WAIT MODE by storing a FFH (held in Register A) into memory location 41FAH (RS-232 Wait Flag).

5D14

LD HL,RSOFF

Let Register Pair HL equal 5F22H, which is a pointer to the message “RS-232 IS OFF”.

“SETOUT”
5D17

PUSH HL

Save the pointer to the message “RS-232 IS OFF” (held in Register Pair HL) to the top of the stack.

5D18

CALL 005AH
[005AH]

GOSUB to 005AH, which is the Model III ROM routine to Initialize the RS-232-C Interface.

5D1B

POP HL

Restore the pointer to the message “RS-232 IS OFF” (held top of the stack) into Register Pair HL, and then remove the entry from the stack.

5D1C

JP 021BH
[021BH]

5D1FH – SETCOM Routine – Set up the RS-232 Channel.

“SETCO1”
5D1F

CP 28H

Check to see if we are at the start of a parameter list by comparing the value held in Register A against 28H (ASCII: (). Results: If Register A equals (, the Z FLAG is set; otherwise the NZ FLAG is set.

5D21

JP NZ,ERR2
[5219H]

If Register A does NOT equal (, then we have a bad character, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5D24

INC HL

Point HL to the next character (the one following the “(“) on the COMMAND LINE by INCrementing the value stored in Register Pair HL by 1.

5D25

LD A,(HL)

Fetch the next character on the COMMAND LINE (held in the memory location pointed to by Register Pair HL) and store it into Register A.

5D26

CP 29H

Compare the value held in Register A against 29H (ASCII: )). Results: If Register A equals 29H ), the Z FLAG is set; otherwise the NZ FLAG is set.

5D28

JR NZ,SETVAL
[5D3DH]

If we didn’t get a “)” then the NZ FLAG (Not Zero) will have been set, set the values by JUMPing to 5D3DH.

5D2A

LD A,0A4H

Let Register A equal 0A4H (1010 0100). This would be Even Parity, Word Length = 7, 1 Stop Bit, Parity On, Send Break Signal, Request to Send On, Data Terminal Ready.

5D2C

LD (41F9H),A

Store the bit pattern 1010 0100 (held in Register A) into memory location 41F9H.

5D2F

LD A,55H

Let Register A equal 55H (0101 0101).

5D31

LD (41F8H),A

Store the bit pattern 0101 0101 (held in Register A) into memory location 41F8H to set the SEND and RECEIVE BAUD RATE to 300.

5D34

LD (41FAH),A

Store the bit pattern 0101 0101 (held in Register A) into memory location 41FAH to turn on the WAIT FLAG.

5D37

CALL 005AH
[005AH]

GOSUB to 005AH, which is the Model III ROM routine to Initialize the RS-232-C Interface.

5D3A

JP SHOTEL
[5C84H]

JUMP back to the RS-232 display status at 5C84H.

5D3DH – SETCOM Routine – Set up the RS-232 Channel – Jumped to if we didn’t get an OPEN PARENTHESIS when we expected it.

“SETVAL”
5D3D

DEC HL

Back HL up to point to the (ASCII: () on the COMMAND LINE.

5D3E

LD DE,SETSWT

Let Register Pair DE equal 5E11H which is the PARSER TABLE for valid SETCOM commands.

5D41

CALL 4454H
[4454H]

GOSUB to 4454H.
NOTE: 4454H is the DOS PARAMETER STRING PARSE routine. It decodes DOS LIBRARY parameters.

5D44

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5D47

LD HL,(SOFF)

Fetch the value held in memory location 5E03H (the RS-232 ON/OFF FLAG) and store it into Register Pair HL.

5D4A
5D4A

LD A,H
OR L

5D4C

JR NZ,SETOFF
[5D09H]

If RS-232 is off, then the NZ FLAG (Not Zero) will have been set, JUMP to 5D09H.

5D4E

LD HL,(5E0DH)

Fetch the value held in memory location 5E0DH (the WAIT FLAG) and store it into Register Pair HL.

5D51
5D51

LD A,H
OR L

5D53

JR Z,SETVA1
[5D5AH]

If the WAIT FLAG is on, then the Z FLAG (Zero) will have been set, JUMP to 5D5AH.

“SETWAT”
5D55

LD (WAIT),A

Store the value held in Register A into memory location 41FAH (which is the storage location for is the storage location for the RS-232 Wait Flag. 0=Wait, 1=No Wait).

5D58

JR SETVA2
[5D64H]

Set the value and continue by JUMPing to 5D64H.

5D5AH – SETCOM Routine – Reset WAIT Mode.

“SETVA1”
5D5A

LD HL,(SSWAIT)

Fetch the value held in memory location 5E0FH (the “NO WAIT” FLAG) and store it into Register Pair HL.

5D5D
5D5D

LD A,H
OR L

5D5F

JR Z,SETVA2
[5D64H]

If it is already ZERO JUMP to 5D64H.

5D61

XOR A

Set Register A to ZERO and clear all Flags.

5D62

JR SETWAT
[5D55H]

JUMP to 5D55H to continue.

5D64H – SETCOM Routine – Set the Baud Rate and Stop Bits.

“SETVA2”
5D64

LD BC,(SBAUD)

Fetch the value held in memory location 5E05H (the BAUD RATE FLAG) and store it into Register Pair BC.

5D68
5D68

LD A,B
OR C

5D6A

JR Z,SETVA4
[5D86H]

If the BAUD RATE is already ZERO, JUMP to 5D86H.

5D6C

LD HL,BADTAB

Let Register Pair HL equal 5E4AH, which is the top of the BAUD RATE LOOKUP TABLE.

“SETVA3”
5D6F

LD A,(HL)

Fetch the character in the BAUD RATE LOOKUP TABLE (held in the memory location pointed to by Register Pair HL) and store it into Register A.

5D70

CP 0FFH

Compare the value held in Register A against the end of table terminator byte (i.e., 0FFH). Results: If Register A equals 0FFH, the Z FLAG is set; otherwise the NZ FLAG is set.

5D72

JP Z,ERR2
[5219H]

If we ran out of entries then the Z FLAG (Zero) will have been set, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5D75

LD E,(HL)

Fetch the LSB of the 2 byte baud rate code (held in the memory location pointed to by Register Pair HL) and store it into Register E.

5D76

INC HL

INCrement the table pointer (stored in Register Pair HL) by 1. HL should now be pointing to the MSB of the baud rate code.

5D77

LD D,(HL)

Fetch the MSB of the 2 byte baud rate code (held in the memory location pointed to by Register Pair HL) and store it into Register E.

5D78

INC HL

INCrement the table pointer (stored in Register Pair HL) by 1. HL should now be pointing to the value associated with that baud rate.

5D79

INC HL

INCrement the value stored in Register Pair HL by 1. HL should now be pointing to the LSB of the next baud rate in the table.

5D7A

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5D7B

EX DE,HL

EXchange the value stored in Register Pair HL (the pointer to the next entry in the BAUD RATE TABLE) with the value stored in Register Pair DE (the last decoded baud rate).

5D7C

SBC HL,BC

Check to see if the table entry matches what the user entered via subtracting the value stored in Register Pair BC and the carry flag from the value stored in Register Pair HL.

5D7E

EX DE,HL

EXchange the value stored in Register Pair HL (the last decoded baud rate) with the value stored in Register Pair DE (the pointer to the next entry in the BAUD RATE TABLE).

5D7F

JR NZ,SETVA3
[5D6FH]

If there was no match, then the NZ FLAG (Not Zero) will have been set, JUMP to 5D6FH to look at the next entry in the table.

5D81

DEC HL

DECrement the value stored in Register Pair HL by 1 to now point to the value associated with the match (which is the BAUD RATE in the table entry).

5D82

LD A,(HL)

Fetch the value held in the memory location pointed to by Register Pair HL and store it into Register A.

5D83

LD (41F8H),A

Store the value from the table which matched the selected baud rate (held in Register A) into memory location 41F8H (which is the Model III storage location for the TRANSMIT and RECEIVE Baud Rate).

“SETVA4”
5D86

LD HL,(SSTOP)

Fetch the value held in memory location 5E09H (i.e., the NUMBER OF STOP BITS) and store it into Register Pair HL.

5D89
5D89

LD A,H
OR L

5D8B

JR Z,SETVA5
[5D96H]

If the Z FLAG (Zero) has been set, then no stop bits were given, so JUMP to 5D96H to continue.

5D8D

DEC L

Start testing to see if ONE stop bit was given by DECrementing the LSB of the STOP BIT value stored in Register L by 1.

5D8E

LD B,10H

Let Register B equal a mask of 10H (0001 0000).

5D90

CALL Z,UNSET
[5DFAH]

If Register L was already at 0, then we had ONE STOP BIT, and we need to clear that bit via a GOSUB to 5DFAH.

5D93

CALL NZ,SETBYT
[5DF1H]

If result from that GOSUB set the NZ FLAG -or- Register L was not already at 0, then we have two stop bits, and we need to set that bit via a GOSUB to 5DF1H.

“SETVA5”
5D96

LD HL,(SPAR)

Fetch the value held in memory location 5E0BH (i.e., the PARITY) and store it into Register Pair HL.

5D99
5D99

LD A,H
OR L

5D9B

LD B,08H

Let Register B equal a mask of 08H (0000 1000).

5D9D

JR Z,SETVA6
[5DB5H]

If the PARITY was already at 0, JUMP to 5DB5H.

5D9F

LD A,L

Copy the Parity Value (held in Register L) into Register A.

5DA0

CP 03H

Compare the value held in Register A against 03H. Results: If Register A equals 03H (Parity = NONE), the Z FLAG is set; otherwise the NZ FLAG is set.

5DA2

JR NZ,SETV50
[5DA9H]

If the NO PARITY set has NOT been set, the NZ FLAG (Not Zero) will have been set, JUMP to 5DA9H to set the parity.

5DA4

CALL SETBYT
[5DF1H]

GOSUB to 5DF1H to set the Parity = NONE bit.

5DA7

JR SETVA6
[5DB5H]

JUMP to 5DB5H to continue.

5DA9H – SETCOM Routine – Set the Parity and Word Length.

“SETV50”
5DA9

CALL UNSET
[5DFAH]

Reset the PARITY BIT via a GOSUB to 5DFAH.

5DAC

DEC L

Check to see if the PARITY was set to ODD by DECrementing the value stored in Register L by 1 so bt the parity type (odd or even).

5DAD

LD B,80H

Let Register B equal a mask of 80H (1000 0000).

5DAF

CALL Z,UNSET
[5DFAH]

If the DEC resulted in a 0, then clear the bit via a GOSUB to 5DFAH.

5DB2

CALL NZ,SETBYT
[5DF1H]

If the NZ FLAG (Not Zero) has been set, then set the bit via a GOSUB to 5DF1H.

“SETVA6”
5DB5

LD HL,(SWORD)

Fetch the WORD LENGTH (held in memory location 5E07H) and store it into Register Pair HL.

5DB8
5DB8

LD A,H
OR L

5DBA

JR Z,SETVA9
[5DE1H]

If the WORD LENGTH storage location was a 0, JUMP to 5DE1H.

5DBC

LD B,60H

Let Register B equal a mask of 60H (0110 0000).

5DBE

CALL UNSET
[5DFAH]

Clear the word length bits via a GOSUB to 5DFAH.

5DC1

LD A,L

Copy the contents of Register L (the length) into Register A.

5DC2

SUB 05H

SUBtract the value 05H from Register A to leave A in the range of 00-03.

5DC4

JP C,ERR2
[5219H]

If the starting value was too low, then the C FLAG (Carry) has been set, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5DC7

JR Z,SETVA9
[5DE1H]

If the resulting value is 00, then we have 5 bits so JUMP to 5DE1H.

5DC9

LD L,A

Copy the subtracted contents of Register A back into Register L.

5DCA

DEC L

DECrement the value stored in Register L by 1. IF L is 0 then we have 6 bits.

5DCB

JR NZ,SETVA7
[5DD1H]

If we have MORE than 6 bits, the NZ FLAG (Not Zero) will have been set, so JUMP to 5DD1H.

5DCD

LD B,40H

Let Register B equal a mask of 40H (0100 0000).

5DCF

JR SETVAA
[5DDEH]

Set the mask of 6 bits via a JUMP to 5DDEH.

5DD1H – SETCOM Routine – Set the Word Length if 7 Bits.

“SETVA7”
5DD1

DEC L

DECrement the value stored in Register L by 1. IF L is 0 then we have 7 bits.

5DD2

JR NZ,SETVA8
[5DD8H]

If we don’t have 7 bits the NZ FLAG (Not Zero) will have been set, JUMP to 5DD8H.

5DD4

LD B,20H

Let Register B equal a mask of 20H (0010 0000).

5DD6

JR SETVAA
[5DDEH]

Set a mask of 7 bits via a JUMP to 5DDEH.

5DD8H – SETCOM Routine – Set the Word Length if 8 Bits.

“SETVA8”
5DD8

DEC L

DECrement the value stored in Register L by 1. IF L is 0 then we have 8 bits.

5DD9

JP NZ,ERR2
[5219H]

If we don’t have 8 bits then the NZ FLAG (Not Zero) will have been set, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5DDC

LD B,60H

Let Register B equal a mask of 60H (0110 0000).

“SETVAA”
5DDE

CALL SETBYT
[5DF1H]

Set a mask of 8 bits via a GOSUB to 5DF1H.

“SETVA9”
5DE1

LD A,(41F9H)

Fetch the RS-232 Configuration Byte (in memory location 41F9H) and store it into Register A.

5DE4

AND 0FCH

MASK the value of Register A against 0FCH (1111 1100). This has the effect of turning off bits 1 (Request to Send) and 0 (Data Terminal Ready).

5DE6

OR 04H

OR Register A against 04H (0000 0100). This has the effect of turning on bit 2 (TRANSMIT = Enable).

5DE8

LD (41F9H),A

Store the revised value held in Register A into memory location 41F9H.

5DEB

CALL 005AH
[005AH]

GOSUB to 005AH, which is the Model III ROM routine to Initialize the RS-232-C Interface.

5DEE

JP SHOTEL
[5C84H]

Display the resulting revised RS-232 settings and RETurn via a JUMP to 5C84H.

5DF1H – SETCOM Routine – Set the configuration bits of the RS-232 based on the mask held in Register B.

“SETBYT”
5DF1

LD A,(41F9H)

Fetch the RS-232 Configuration Byte (held in memory location 41F9H) and store it into Register A.

5DF4

OR B

Apply the mask held in Reigster B via ORing Register B against Register A. The results are stored in Register A.

“SETBY1”
5DF5

LD (41F9H),A

Store the revised RS-232 Configuration Byte (value held in Register A) into memory location 41F9H.

5DF8

XOR A

Set Register A to ZERO and clear all Flags.

5DF9

RET

RETurn to the caller.

5DFAH – SETCOM Routine – Reset the configuration bits of the RS-232 based on the mask held in Register B.

“UNSET”
5DFA

LD A,B

Copy the mask (held in Register B on entry) into Register A.

5DFB

CPL

Reverse each bit in Register A (which is the same as NOT).

5DFC

LD B,A

Put the modified mask back into Register B.

5DFD

LD A,(41F9H)

Fetch the RS-232 Configuration Byte (held in memory location 41F9H) and store it into Register A.

5E00

AND B

MASK the value of Register A against the value held in Register B to turn off all the undesired bits.

5E01

JR SETBY1
[5DF5H]

JUMP to 5DF5H to finish.

5E03H – MESSAGE and BYTE STORAGE for SETCOM.

“SOFF”
5E03

DEFW 0000H

RS-232 ON/OFF FLAG.

“SBAUD”
5E05

DEFW 0000H

BAUD RATE FLAG.

“SWORD”
5E07

DEFW 0000H

WORD LENGTH.

“SSTOP”
5E08

DEFW 0000H

NUMBER OF STOP BITS.

“SPAR”
5E0B

DEFW 0000H

PARITY SETTING.

“SWAIT”
5E0D

DEFW 0000H

“WAIT” FLAG.

“SSWAIT”
5E0F

DEFW 0000H

“NO WAIT” FLAG.

5E11H – PARSER TABLE for SETCOM.

“SETSWT”
5E11

DEFM “OFF “

5El9

DEFM “BAUD “

5E21

DEFM “WORD “

5E29

DEFM “STOP “

5E31

DEFM “PARITY”

5E39

DEFM “WAIT “

5E41

DEFM “NOWAIT”

5E49

DEFB 00H

Table Terminator

5E4AH – BAUD RATE TABLE for SETCOM.

“BADTAB”
5E4A

DEFB 50H 00H 00H

Baud Rate of 50

5E4D

DEFB 75H 00H 11H

Baud Rate of 75

5E50

DEFB 10H 01H 22H

Baud Rate of 110

5E53

DEFB 34H 01H 33H

Baud Rate of 134.5

5E56

DEFB 50H 01H 44H

Baud Rate of 150

5E59

DEFB 00H 03H 55H

Baud Rate of 300

5E5C

DEFB 00H 06H 66H

Baud Rate of 600

5E5F

DEFB 00H 12H 77H

Baud Rate of 1200

5E62

DEFB 00H 18H 88H

Baud Rate of 1800

5E65

DEFB 00H 20H 99H

Baud Rate of 2000

5E68

DEFB 00H 24H AAH

Baud Rate of 2400

5E6B

DEFB 00H 36H BBH

Baud Rate of 3600

5E6E

DEFB 00H 48H CCH

Baud Rate of 4800

5E71

DEFB 00H 72H DDH

Baud Rate of 7200

5E74

DEFB 00H 96H EEH

Baud Rate of 9600

5E77

DEFB FFH FFH

End of Table Designator

5E79H – Word Length Text Pointer Table.

“TABLE1”
5E79

DEFW D6H 5EH

Pointer to the ASCII Text corresponding to a Word Length of 5

5E7B

DEFW D8H 5EH

Pointer to the ASCII Text corresponding to a Word Length of 6

5E7D

DEFW DAH 5EH

Pointer to the ASCII Text corresponding to a Word Length of 7

5E7F

DEFW DCH 5EH

Pointer to the ASCII Text corresponding to a Word Length of 8

5E81H – Baud Rate Text Pointer Table.

“TABLE2”
5E81

DEFW DEH 5EH

Pointer to the ASCII Text corresponding to a Baud Rate of 50

5E83

DEFW E1H 5EH

Pointer to the ASCII Text corresponding to a Baud Rate of 75

5E85

DEFW E4H 5EH

Pointer to the ASCII Text corresponding to a Baud Rate of 110

5E87

DEFW E8H 5EH

Pointer to the ASCII Text corresponding to a Baud Rate of 134.5

5E89

DEFW EEH 5EH

Pointer to the ASCII Text corresponding to a Baud Rate of 150

5E8B

DEFW F2H 5EH

Pointer to the ASCII Text corresponding to a Baud Rate of 300

5E8D

DEFW F6H 5EH

Pointer to the ASCII Text corresponding to a Baud Rate of 600

5E8F

DEFW FAH 5EH

Pointer to the ASCII Text corresponding to a Baud Rate of 1200

5E91

DEFW FFH 5EH

Pointer to the ASCII Text corresponding to a Baud Rate of 1800

5E93

DEFW 04H 5FH

Pointer to the ASCII Text corresponding to a Baud Rate of 2000

5E95

DEFW D9H 5FH

Pointer to the ASCII Text corresponding to a Baud Rate of 2400

5E97

DEFW 0EH 5FH

Pointer to the ASCII Text corresponding to a Baud Rate of 3600

5E99

DEFW 13H 5FH

Pointer to the ASCII Text corresponding to a Baud Rate of 4800

5E9B

DEFW 18H 5FH

Pointer to the ASCII Text corresponding to a Baud Rate of 7200

5E9E

DEFW 1DH 5FH

Pointer to the ASCII Text corresponding to a Baud Rate of 9600

5E9FH – MESSAGE DISPLAY for SETCOM CONFIGURATION.

“BAUDMG”
5E9F

DEFM “BAUD” + 03H

Configuration Element

“UARTMG”
5EA4

DEFM “WORD” + 03H

Configuration Element

“STOPMG”
5EA9

DEFM “STOP” + 03H

Configuration Element

“PARTMG”
5EAE

DEFM “PARITY” + 03H

Configuration Element

“NONE”
5EB5

DEFM “NONE” + 03H

Parity Classes

“ODD”
SEBA

DEFM “ODD” + 03H

Parity Classes

“EVEN”
5EBE

DEFM “EVEN” + 03H

Parity Classes

“WAITS”
5EC3

DEFM “WAIT” + 03H

Wait States

“NWAITS”
5EC8

DEFM “NO WAIT” + 03H

Wait States

“SMODE”
5ED0

DEFM “MODE” + 0DH

“S5”
5ED6

DEFM “5” + 03H

Word Length

“S6”
5ED8

DEFM “6” + 03H

Word Length

“S7”
SEDA

DEFM “7” + 03H

Word Length

“S8”
5EDC

DEFM “8” + 03H

Word Length

“S50”
5EDE

DEFM “50” + 03H

Baud Rate Table

“S75”
5EE1

DEFM “75” + 03H

Baud Rate Table

“S110”
5EE4

DEFM “110” + 03H

Baud Rate Table

“S134”
5EE8

DEFM “134.5” + 03H

Baud Rate Table

“S150”
SEEE

DEFM “150” + 03H

Baud Rate Table

“S300”
5EF2

DEFM “300” + 03H

Baud Rate Table

“S600”
5EF6

DEFM “600” + 03H

Baud Rate Table

“S1200”
SEFA

DEFM “1200” + 03H

Baud Rate Table

“S1800”
SEFF

DEFM “1800” + 03H

Baud Rate Table

“S2000”
5F04

DEFM “2000” + 03H

Baud Rate Table

“S2400”
5F09

DEFM “2400” + 03H

Baud Rate Table

“S3600”
SFOE

DEFM “3600” + 03H

Baud Rate Table

“S4800”
5Fl3

DEFM “4800” + 03H

Baud Rate Table

“S7200”
5Fl8

DEFM “7200” + 03H

Baud Rate Table

“S9600”
5FlD

DEFM “9600” + 03H

Baud Rate Table

“RSOFF”
5F22

DEFM “RS-232 IS NOW OFF” + 0DDH

Message.

5F34H – “DUAL” Routine – Output to BOTH the Printer and the Display

First, check to see if ROUTE is on.

“DUAL”
5F34

LD A,(442FH)

Fetch the DUAL status byte (held in memory location 442FH) and store it into Register A. 80H=ROUTE, FFH=DUAL, 00H=Neither.

5F37

CP 80H

Compare the value held in Register A against 80H. Results: If Register A equals 80H, the Z FLAG is set; otherwise the NZ FLAG is set.

5F39

JR Z,NODUAL
[5F88H]

If A = 80H then ROUTE is active and the the Z FLAG (Zero) will have been set, JUMP to 5F88H.

5F3B

CALL CHKFLG
[5081H]

Evaluate the DUAL parameter via a GOSUB to 5081H.

5F3E

JR Z,DUALOF
[5F64H]

If the CALL returned with the Z FLAG set, the “OFF” parameter was provided; JUMP to 5F64H.

Next, check to see if DUAL is already on.

5F40

LD A,(442FH)

Fetch the DUAL status byte (held in memory location 442FH) and store it into Register A. 80H=ROUTE, FFH=DUAL, 00H=Neither.

5F43

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5F44

JR NZ,DUALON
[5F5FH]

If the DUAL status was already on the NZ FLAG (Not Zero) will have been set, just display the DUAL ON message again via a JUMP to 5F5FH.

If we’re here, then we actually need to process the DUAL command.

5F46

DEC A

DECrement the value stored in Register A by 1 to go from the 00H to FFH.

5F47

LD (442FH),A

Store the FFH (DUAL mode ON) (held in Register A into memory location 442FH.

5F4A

LD HL,(401EH)

Fetch the video driver address (held in memory location 401EH) and store it into Register Pair HL.

5F4D

LD (4CE7H),HL

Store the video driver address (held in Register Pair HL) into the system memory location for DUAL’s video driver (i.e., 4CE7H).

5F50

LD HL,(4026H)

Fetch the printer driver address (held in memory location 4026H) and store it into Register Pair HL.

5F53

LD (4CF8H),HL

Store the printer driver address (held in Register Pair HL) into the system memory location for DUAL’s printer driver (i.e., 4CF8H).

5F56

LD HL,4CE1H

Let Register Pair HL equal 4CE1H, which is the code for the DUAL routine.

5F59

LD (401EH),HL

Store 4CE1H (held in Register Pair HL) into the DUAL routine’s video driver address (held at memory location 401EH).

5F5C

LD (4026H),HL

Store 4CE1H (held in Register Pair HL) into the DUAL routine’s printer driver address (held at memory location 4026H).

“DUALON”
5F5F

LD HL,5FD2H

Let Register Pair HL equal 5FD2H, to point to the message “ON”.

5F62

JR DULPRT
[5F7DH]

JUMP to 5F7DH.

5F64H – “DUAL” Routine – Restore

“DUALOF”
5F64

LD A,(442FH)

Fetch the DUAL status byte (held in memory location 442FH) and store it into Register A. 80H=ROUTE, FFH=DUAL, 00H=Neither.

5F67

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5F68

JR Z,DUALO1
[5F7AH]

If DUAL was already off (i.e., A was already 00), then there is nothing to process, so just display the DUAL OFF message via a JUMP to 5F7AH.

If we are here, then we need to process a DUAL OFF command.

5F6A

LD HL,(4CE7H)

Copy the video driver address (held in memory location 4CE7H for safe keeping) in Register Pair HL.

5F6D

LD (401EH),HL

Store the backed-up video driver address (held in HL) and into the video driver address (held in memory location 401EH).

5F70

LD HL,(4CF8H)

Copy the printer driver address (held in memory location 4CF8H for safe keeping) in Register Pair HL.

5F73

LD (4026H),HL

Store the backed-up printer driver address (held in HL) and into the printer driver address (held in memory location 4026H).

5F76

XOR A

Set Register A to ZERO and clear all Flags.

5F77

LD (442FH),A

Set the DUAL status byte (held in memory location 442FH) and to 00H. 80H=ROUTE, FFH=DUAL, 00H=Neither.

“DUALO1”
5F7A

LD HL,5FD5H

Let Register Pair HL equal 5FD5H, to point to the message “OFF”.

“DULPRT”
5F7D

PUSH HL

Save the contents of Register Pair HL to the top of the stack.

5F7E

LD HL,DULMSG

Let Register Pair HL equal 5FC5H, to point to the message “DUAL IS NOW “.

5F81

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

5F84

POP HL

Put the value held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

5F85

JP 021BH
[021BH]

5F88H – “DUAL” Routine – Abort if DUAL is engaged while ROUTE is engaged.

“NODUAL”
5F88

LD HL,NODMSG

Let Register Pair HL equal 5F95H, to point to the message “CAN’T ACTIVATE DUAL WHILE ROUTE IS IN OPERATION“.

5F8B

JP 021BH
[021BH]

5F8EH – Get the next COMMAND LINE character.

“SKIPSP”
5F8E

LD A,(HL)

Fetch the value held in the memory location pointed to by Register Pair HL and store it into Register A.

5F8F

CP 20H

Compare the value held in Register A against 20H (0010 0000) / (Decimal: 32)(ASCII: SPACE).

5F91

RET NZ

If the NZ FLAG (Not Zero) has been set, RETurn to the caller.

“SKIPS1”
5F92

INC HL

INCrement the value stored in Register Pair HL by 1.

5F93

JR SKIPSP
[5F8EH]

Loop back to the top of this routine.

5F95H – MESSAGE and BYTE STORAGE for DUAL.

“NODMSG”
5F95

DEFM →

“CAN’T ACTIVATE DUAL WHILE ROUTE IS IN OPERATION“.

“DULMSG”
5FC5

DEFM →

“‘DUAL IS NOW’ + 03H“.

“ON”
5FD2

DEFM →

“‘ON’ + 0DH“.

“OFF”
5FD5

DEFM →

“‘OFF’ + 0DH“.

5FD9H – “WP” Routine – Set a drive as write protected.

“WPROT”
5FD9

CALL SKIPSP
[5F8EH]

Get the next non-space COMMAND LINE character via a GOSUB to 5F8EH.

5FDC

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN, the Z FLAG is set; otherwise the NZ FLAG is set.

5FDE

JR NZ,WPROT1
[5FE4H]

If there were parameters on the COMMAND LINE (which would be a drive number) the NZ FLAG (Not Zero) will have been set, so skip over the next 2 instructions which set the value if no disk drive is given.

5FE0

LD A,0FFH

Let Register A equal 0FFH.

5FE2

JR WPROT3
[600CH]

JUMP to 600CH to set the drive number held in Register A into the middle of an opcode in SYS00/SYS which checks for write protect against FFH before permitting a write.

5FE4H – “WP” Routine – Jumped here if there were parameters given.

“WPROT1”
5FE4

LD DE,WPSW

Let Register Pair DE equal 6010H to point to the COMMAND PARSER TABLE for the WP COMMAND.

5FE7

CALL 4454H
[4454H]

GOSUB to 4454H.
NOTE: 4454H is the DOS PARAMETER STRING PARSE routine. It decodes DOS LIBRARY parameters.

5FEA

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

5FED

LD BC,(WPDRV)

Let Register Pair BC equal the drive number (which was put into 5FEE-5FEFH elsewhere in the overlay).

5FF0

LD A,(4413H)

Fetch the maximum number of drives in the system (held in memory location 4413H) and store it into Register A.

5FF3

CP C

Compare the drive number given (held in Register C) against the highest drive number on the system (held in Register A). Results:

If Register A equals the value held in Register C, the Z FLAG is set.
If A < C, the CARRY FLAG will be set.
if A >= C, the NO CARRY FLAG will be set.

5FF4

JP C,ERR9
[5221H]

If the requested drive number (in C) is equal to or higher than the highest drive number (in A) the C FLAG (Carry) will have been set, JUMP to 5221H with an error.

5FF7

LD A,C

Copy the requested drive number from Register C into Register A.

5FF8

ADD A,30H

LET Register A = Register A + 30H. Note: Adding 30H to from Register A will convert decimal number 0-9 into its ASCII equivalent (i.e., 6 + 30H = 36H, which, in ASCII, is 6.

5FFA

LD (WPDR),A

Store the value held in Register A into memory location 6024H which is in the middle of the “DISK DRIVE _ IS NOW” message.

5FFD

PUSH BC

Save the drive number (held in Register Pair BC) to the top of the stack.

5FFE

LD HL,WPDMSG

Let Register Pair HL equal 6019H, which is the message “DISK DRIVE _ IS NOW” + 03H.

6001

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

6004

LD HL,FINMSG

Let Register Pair HL equal 602EH, which is the message “WRITE PROTECTED”.

6007

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

600A

POP BC

Restore the drive number from the top of the STACK into Register Pair BC, and then remove the entry from the stack.

600B

LD A,C

Copy the drive number from Register C into Register A.

“WPROT3”
600C

LD (45F8H),A

Store the value held in Register A into memory location 45F8H which in the middle of an opcode in the SYS00/SYS routine which checks for write protect before doing a write.

600F

RET

RETurn to the caller.

6010H – PARSER TABLE for WP COMMAND.

“WPSW”
6010

DEFM “DRIVE “

6016

DEFW EEH 5FH

This is the memory address in the middle of a LD BC,(____) OPCODE where the disk drive number is stored

6018

DEFB 00H

End of Table Delimiter.

“WPDMSG”
6019

DEFM →

“‘DISK DRIVE 0 IS NOW ‘ + 03H“. Note that the “0” is “WPDR”

“FINMSG”
602E

DEFM →

“‘WRITE PROTECTED ‘“.

603EH – “MASTER” Routine. This routine re-assigns the master drive number.

“MASTER”
603E

CALL SKIPSP
[5F8EH]

Get the next non-space COMMAND LINE character via a GOSUB to 5F8EH.

6041

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN then we got the command but no parameters (i.e., just typed in MASTER), the Z FLAG is set; otherwise the NZ FLAG is set.

6043

JR NZ,6048H
[6048H]

If parameters (which would be a drive number) were given, then the NZ FLAG (Not Zero) will have been set, so skip over the next 2 instructions which put in a default drive number.

6045

XOR A

Set Register A to ZERO and clear all Flags, thus setting Register A to a default of DRIVE 0.

6046

JR 6071H
[6071H]

JUMP to 6071H to put a 0 into the system storage location of the MASTER DRIVE NUMBER.

6048H – “MASTER” Routine – Jumped here if there were parameters given.

“MAST1”
6048

LD DE,WPSW

Let Register Pair DE equal 6010H which is the parser table for the WP command, focusing on the drive number.

604B

CALL 4454H
[4454H]

GOSUB to 4454H.
NOTE: 4454H is the DOS PARAMETER STRING PARSE routine. It decodes DOS LIBRARY parameters.

604E

JP NZ,ERR2
[5219H]

If the NZ FLAG (Not Zero) has been set, then the CALL produced an error, so JUMP to 5219H to report an ILLEGAL COMMAND PARAMETER error, and ABORT.

6051

LD BC,(WPDRV)

Fetch the drive number (held in memory location 5FEEH) and store it into Register Pair BC.

6055

LD A,(4413H)

Fetch the maximum number of drives in the system (held in memory location 4413H) and store it into Register A.

6058

CP C

Compare the drive number given (held in Register C) against the highest drive number on the system (held in Register A). Results:

If Register A equals the value held in Register C, the Z FLAG is set.
If A < C, the CARRY FLAG will be set.
if A >= C, the NO CARRY FLAG will be set.

6059

JP C,5221H
[5221H]

If the requested drive number (in C) is equal to or higher than the highest drive number (in A) the C FLAG (Carry) will have been set, JUMP to 5221H with an error.

605C

LD A,C

Copy the requested drive number from Register C into Register A.

605D

ADD A,30H

LET Register A = Register A + 30H. Note: Adding 30H to from Register A will convert decimal number 0-9 into its ASCII equivalent (i.e., 6 + 30H = 36H, which, in ASCII, is 6.

605F

LD (WPDR),A

Store the value held in Register A into memory location 6024H which is in the middle of the “DISK DRIVE _ IS NOW” message.

6062

PUSH BC

Save the drive number (held in Register Pair BC) to the top of the stack.

6063

LD HL,WPDMSG

Let Register Pair HL equal 6019H, which is the message “DISK DRIVE _ IS NOW” + 03H.

6066

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

6069

LD HL,MSTMSG

Let Register Pair HL equal 6075H, which is the pointer to the message “THE MASTER DRIVE”.

606C

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

606F

POP BC

Restore the drive number from the top of the STACK into Register Pair BC, and then remove the entry from the stack.

6070

LD A,C

Copy the drive number from Register C into Register A.

“MAST2”
6071

LD (42B3H),A

Store the disk drive (held in Register A) into memory location 42B3H which is the storage location for the MASTER DRIVE NUMBER.

6074

RET

RETurn to the caller.

6075H – MESSAGE and BYTE STORAGE for MASTER.

“MSTMSG”
6075

DEFM →

“‘THE MASTER DRIVE’ + 0DH“.

6086H – Convert Binary Coded Decimal into a Binary Value. On Entry HL = a hex value and On Exit HL = the decimal value.

“CONVHX”
6086

EX DE,HL

EXchange the value stored in Register Pair HL (the number to convert) with the value stored in Register Pair DE (irrelevant).

6087

LD A,D

Copy the MSB of the number to convert (held in Register D) into Register A.

6088

CALL SHIFT
[60B5H]

Rotate Register A left 4 times to the HIGH NYBBLE via a GOSUB to 60B5H.

608B
608C

LD L,A
LD H,00H

Let Register Pair HL = the high nybble of the MSB of the requested value (held in Register A).

608E
608F

PUSH HL
POP BC

Let BC = the high nybble of the MSB of the requested value (held in Register Pair HL).

“”
6090

CALL ADDHL
[60B0H]

Multiply the high nybble of the MSB by 10 via a GOSUB to 60B0H.

Now the high nybble of the MSB has been shifted over to the 10’s spot, so that the low nybble of the MSB can occupy the 1’s spot.

6093

LD A,0FH

Let Register A equal a mask of 0FH (0000 1111).

6095

AND D

MASK the value of Register A against the MSB of the number to convert (held in Register D) to isolate the low nybble.

6096

LD C,A

Let Register C = the low nybble of the MSB of the requested value (held in Register A).

6097

ADD HL,BC

LET Register Pair HL = 10 * the High Nybble of the MSB + the Low Nybble of the MSB.

6098
6099

PUSH HL
POP BC

LET Register Pair BC = 10 * the High Nybble of the MSB + the Low Nybble of the MSB.

609A

CALL ADDHL
[60B0H]

Multiply that by 10 via a GOSUB to 60B0H (results in HL).

Now the converted MSB has been shifted over to the 10’s spot, so that the LSB can occupy the 1’s spot.

609D

LD A,E

Copy the LSB of the number to convert (held in Register D) into Register A.

609E

CALL SHIFT
[60B5H]

Rotate Register A left 4 times to the LOW NYBBLE via a GOSUB to 60B5H.

60A1
60A2

LD C,A
LD B,00H

Let BC = the high nybble of the LSB of the requested value (held in Register Pair HL).

60A4

ADD HL,BC

LET Register Pair HL = the prior total (held in Register Pair HL) + the high nybble of the LSB (held in Register BC).

60A5
60A6

PUSH HL

PUSH HL
POP BC

LET Register Pair BC = 10 * that total.

Now the high nybble of the LSB has been added to the converted MSB.

60A7

CALL ADDHL
[60B0H]

Multiply that by 10 via a GOSUB to 60B0H (results in HL).

Now everything has been pushed over one level, leaving just the 1’s spot empty.

60AA

LD A,0FH

Let Register A equal a mask of 0FH (0000 1111).

60AC

AND E

MASK the value of Register A against the LSB of the number to convert (held in Register E) to isolate the low nybble of the LSB.

60AD

LD C,A

Let Register Pair BC = the low nybble of the LSB of the value to convert.

60AE

ADD HL,BC

LET Register Pair HL = Register Pair HL + Register BC.

60AF

RET

RETurn to the caller.

60B0H – Routine to Multiply HL by 10. Requires HL = BC.

“ADDHL”
60B0

ADD HL,HL

LET Register Pair HL = Register Pair HL + Register HL.

60B1

ADD HL,HL

LET Register Pair HL = Register Pair HL + Register HL.

60B2

ADD HL,BC

LET Register Pair HL = Register Pair HL + Register BC.

60B3

ADD HL,HL

LET Register Pair HL = Register Pair HL + Register HL.

60B4

RET

RETurn to the caller.

60B5H – Get the high nybble.

“SHIFT”
60B5
60B7
60B9
60BB

SRL A
SRL A
SRL A
SRL A

60BD

RET

RETurn to the caller.

END 5200H

MISC – STORAGE BYTES.

S9DCB
6130

DEFS 50

Storage of 50 bytes, which is the length of a disk DCB

S9DCB1
6162

DEFS 50

Storage of 50 bytes, which is the length of a disk DCB

S9DCB2
6194

DEFS 50

Storage of 50 bytes, which is the length of a disk DCB

BUFER1
6300

DEFS 256

Storage of 256 bytes

BUFER2
6400

DEFS 256

Storage of 256 bytes