Model I TRSDOS v2.3 BASIC/CMD Explained

This is a disassembly of TRSDOS v2.3’s BASIC/CMD File. 5200H JP 5C06HJP INIT JUMP to 5C06H 5203H – Message Storage Area – Error Messages – “ERRTAB” 5203H ↳ “ERRTAB” NOP No Operation (Do Nothing) 5204H DEFM ‘NEXT without FOR’ + 00H 5215H DEFM ‘Syntax error’ + 00H 5222H DEFM ‘RETURN without GOSUB’ + 00H 5237H DEFM ‘Out […]

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TRS-80 Tips and Tricks – Tape and File Formats/Structures

Page Index: Tape Structures Level I Tape Format Level II BASIC File Tape Format System Tape Format Editor/Assembler Source Tape Format File Structures CMD File Format Editor/Assembler Source File Format SuperSCRIPSIT Document Files DSK/JV1/JV3 File Structure DMK File Structure Level I Tape Format (Model I and III) Leader   A5 Sync Byte MSB MSB of […]

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Tips and Tricks (Main Menu)

Introduction This section of the web site covers tips and tricks, pning from Level II through determining the geometry of a hard drive. There is no rhyme or reason to why tips are or are not present; as I learn of them, they go here. Unfortunately, there is some mixing and matching between the pages, […]

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TRS-80 DOS – TRSDOS v1.3 – SYS11/SYS Disassembled

General: SYS11/SYS handles the TAPE, PURGE, and LIST library commands. Disassembly:   ORG 5200H “BEGIN”5200 LD A,55H Let Register A equal 55H to set the CLEAR RAM flag. 5202 LD (42B4H),A Store the value held in Register A into memory location 42B4H.NOTE: 42B4H is the storage location for the PROGRAM PROTECT/CLEAR RAM Flag. 5205 XOR […]

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TRS-80 DOS – TRSDOS v1.3 – SYS09/SYS Disassembled

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. […]

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TRS-80 DOS – TRSDOS v1.3 – SYS06/SYS Disassembled

General: SYS6 handles the following DOS Commands: APPEND, ATTRIB, AUTO, BUILD, CLEAR, CLOCK, CREATE, DATE, DIR, DO, DUMP, ERROR, FREE, LIB, LOAD, PAUSE, PROT, RENAME, and TIME On Entry, Register C must hold the order number of the command and Register Pair HL the Buffer Input Line. Disassembly:   ORG 5200H “BEGIN”5200 PUSH HL Save […]

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TRS-80 DOS – TRSDOS v1.3 – Internals

Page Menu: Overview of the TRSDOS v1.3 Directory Structure The Granule Allocation Table The Hash Index Table Directory Entries The File Control Block The System Files/Overlays What each System/Overlay file does Location of each System/Overlay File Calling an Overlay in Assembly Overview of the TRSDOS v1.3 Directory Structure The TRSDOS v1.3 directory is located on […]

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TRS-80 DOS – TRSDOS v1.3 – SYS01/SYS Disassembled

  ORG 4E00H 4E00 AND 0F0H MASK the value of Register A against 0F0H (1111 0000). This has the effect of turning off bits 3, 2, 1, and 0, leaving only bits 7, 6, 5, 4 active. 4E02 CP 90H Compare the value held in Register A against 90H (1001 0000). Results: If Register A […]

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TRS-80 DOS – TRSDOS v1.3 – Disassembled

Overview TRSDOS v1.3 is comprised of a BOOT/SYS bootstrap, and then 15 Overlays (00-14), although there is room for a 16th. The system files do not have corresponding directory entries. Rather, they appear at byte E0H in the HIT table just as a string of hex pairs, in the order of the overlay. The first […]

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