TRS-80 DOS - LDOS 5.3.1 for the Model I - DATECONV/CMD Disassembled

DATECONV/CMD

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LDOS 5.3.1 DATECONV/CMD Disassembly - Date-Format Conversion Utility (Model I)

DATECONV/CMD converts a diskette created under LDOS 5.1.4 or earlier to the x.3 time and date directory format introduced with LDOS 5.3 and LS-DOS 6.3. The 5.3 series expanded the accepted date range to 1980-1999 and added a modification time stamp to every directory entry; DATECONV rewrites the older directory records so that date and time information is interpreted correctly under 5.3. The command syntax is DATECONV :d, where :d names the drive to convert.

The utility is a transient /CMD load module. The DOS reads its 628-byte image into memory at 5200H and transfers to 5200H with Register Pair HL addressing the command-line tail. DATECONV parses the drive, confirms the pack is mounted and not write-protected through the resident @CKDRV service, and reads the directory cylinder named by the Drive Code Table. It then decides how the disk should be treated: an older non-x.3 disk that is a bootable SYSTEM disk without the required x.3 system files is refused (matching the manual's instruction to first move x.3 system files onto such a disk with BACKUP), while a disk already in the x.3 format has only its blank-user-access-password files touched so that genuine time stamps are protected.

For each in-use primary directory record that carries an old-style date, DATECONV copies the record's three-bit year field into the extended-dating word - the directory field that under LDOS 5.1.4 held the user access-password hash and under 5.3 carries the packed modification time and extended year. It counts each file it updates, walks every directory sector, writes each modified sector back with the deleted-data address mark LDOS uses for directory sectors, sets bit 3 of the Granule Allocation Table configuration word to mark the whole pack as an x.3 dated disk, and prints the number of files updated. Pressing BREAK during the scan aborts the conversion.

DATECONV issues no RST 28H request of its own. Every service it uses is either a TRS-80 Model I ROM low-core routine or a resident SYS0/SYS entry point, so no system overlay loads while it runs and SYS0/SYS alone is sufficient to cross-reference it.

Variables and Self-Modifying Cells

Address Range	Purpose
5348H 1 byte	Drive number patched into the write-sector routine's LD C,00H at 5347H (self-modifying; written at 5222H from the command-line drive).
535AH 1 byte	Drive number patched into the read-sector routine's LD C,00H at 5359H (self-modifying; written at 5225H).
526FH 1 byte	Directory cylinder patched into the LD D,00H at 526EH (self-modifying; written at 5238H from DCT+09H).
52A2H 1 byte	Conversion-mode flag patched into the LD A,00H at 52A1H (self-modifying; written at 5249H). Non-zero on an already-x.3 disk, restricting conversion to blank-access-password records.
52D3H 1 byte	Directory sector-scan limit patched into the LD A,00H at 52D2H (self-modifying; written at 5281H).
52FBH 2 bytes	Saved entry Stack Pointer patched into the LD SP,0000H at 52FAH (self-modifying; written at 5200H).
5472H-5473H 2 bytes	File-conversion counter; incremented at 52BAH for each file updated and formatted into the completion message at 52E9H.
5500H-55FFH 256 bytes	Shared directory sector buffer above the load image, used for every GAT, HIT and directory-record read and write.

Major Routines

Address	Routine	Entry / Exit
5200H	Program Entry and Sign-On Saves the entry stack, prints the banner, and falls into the drive parser.	Entry: HL = command-line tail. Exit: falls through to 520FH.
5284H	Main Conversion Loop Walks every directory sector and record, converting old-style dates and counting updated files.	Entry: D = directory cylinder, drive patched into the read/write routines. Exit: falls into 52D9H.
52FAH	Exit Routine Restores the entry SP and returns success, or diverts to @ABORT on an error under a JCL job.	Entry: HL = return code (0000H/0FFFFH). Exit: RET or JP @ABORT 4030H.
5309H	Decimal Count Formatter Writes a 16-bit value as right-justified ASCII into a five-byte field.	Entry: HL = value, DE = field. Exit: DE preserved.
5322H	Break/Pause Check Freezes on a pending BREAK and preserves the caller's registers and flags.	Entry: none. Exit: Z when no BREAK pending; caller flags preserved across a freeze.
5344H	Write Directory Sector Writes the buffer with a deleted-data mark and verifies it.	Entry: D = cylinder, E = sector, C = drive (patched). Exit: RET on success, JP 5362H on error.
5356H	Read Directory Sector Reads a sector into the buffer, accepting the deleted-data mark as success.	Entry: D = cylinder, E = sector, C = drive (patched). Exit: RET on success, HL = 5500H.
5362H	Error Display via @ERROR Displays the system message for the code in Register A and exits with an error code.	Entry: A = error code. Exit: JP 5377H then 52FAH.
5369H	Message Error Stubs Three overlapping entries that display the system-disk, write-protected and abort messages.	Entry: 5369H/536DH/5371H. Exit: JP 52FAH.

Cross-Reference Notes

DATECONV/CMD is a transient utility that issues no RST 28H request of its own. It calls the resident SYS0/SYS services @DSPLY (4467H), @CKDRV (44B8H), GETDCT (478FH), WRPROT (4768H), VERSEC (4772H), RDSECT (4777H), @ERROR (4409H), @LOGOT (447BH), @DIV (44C4H) and @ABORT (4030H), and the TRS-80 Model I ROM low-core routines @PAUSE (0060H) and @KBD (002BH). It reads the resident flags KFLAG$ (4423H, the BREAK bit) and SFLAG$ (430FH, the JCL-active bit). No SYS overlay is loaded while it runs, and nothing in the DOS calls into DATECONV.

5200H - Program Entry and Sign-On

DATECONV is a transient /CMD utility. The DOS loads its 628-byte load module into memory at 5200H and transfers to 5200H with Register Pair HL pointing at the command-line text that follows the DATECONV keyword. The routine first preserves the stack so it can return cleanly, prints its sign-on banner through the resident video service, and then falls into the drive parser.

520FH - Command-Line Drive Specification Parse

The command syntax is DATECONV :d. This block skips leading blanks, requires a colon, reads the single drive digit, verifies it is 0-7, and writes it into the drive-number operand of both the sector-read and sector-write routines. A malformed specification jumps to the illegal-drive error stub at 537DH.

5229H - Drive Availability Check

The resident @CKDRV service confirms the drive holds a mounted, ready pack and reports its write-protect status. A missing drive is treated as an illegal drive; a write-protected pack cannot be converted and is reported separately.

5232H - Directory Cylinder, GAT Read and Dating-Flag Test

The Drive Code Table entry gives the directory cylinder. DATECONV reads sector 0 of that cylinder (the Granule Allocation Table) and tests the high byte of the GAT configuration word: bit 3 marks a disk that is already in the x.3 extended-dating format. On such a disk DATECONV skips the system-disk gate and converts only files whose access-password word is still blank, protecting genuine x.3 time stamps.

524EH - System-Disk Detection

On an older non-x.3 disk, DATECONV refuses to convert a bootable SYSTEM disk that does not already carry the x.3 system files, matching the manual: a TRSDOS 6.2, LDOS 5.1 or earlier SYSTEM disk must first have x.3 system files copied onto it with BACKUP. The gate is skipped when bit 7 of the GAT configuration byte marks the pack as exempt, or when the first directory slot examined is unused.

526EH - Directory Sector-Scan Limit

Before the conversion loop, DATECONV works out how many directory sectors it must scan. It reads the third directory sector and derives a sector limit from the ending-record-number field of the record it finds there, capped at 21H, and stores it as the loop bound.

5284H - Main Conversion Loop

This is the core of DATECONV. For each directory sector from sector 2 up to the computed limit, it reads the sector and walks its eight 32-byte records. An in-use primary record that carries an old-style date has the low three date bits copied into its extended-dating word, and on an already-x.3 disk only records whose access-password word is still blank (hash 4296H) are touched. After each sector is scanned it is written back.

52D9H - Mark Disk Dated and Report Completion

With every directory sector converted, DATECONV sets bit 3 of the GAT configuration byte so the pack is recognised as an x.3 extended-dating disk, writes the GAT back, formats the file count into the completion message, displays it, and returns success.

52FAH - Exit Routine

Common exit for both the success and error paths. It restores the entry stack pointer saved at 5200H, then returns to the DOS on success or, when running under a JCL job, diverts to @ABORT on an error code so the job halts.

5309H - Decimal Count Formatter

Converts the 16-bit value in Register Pair HL into right-justified ASCII decimal, written backwards into a five-character field that begins at the buffer addressed by Register Pair DE. The field is first blanked so leading positions stay as spaces.

5322H - Break/Pause Check

Checks the resident KFLAG$ BREAK bit. With no break pending it returns immediately with the Z FLAG set. With a break pending it clears the flag, freezes with a delay, re-freezes if BREAK is pressed again, and waits for a key to be released before continuing; the caller's registers and flags are preserved across the freeze.

5344H - Write Directory Sector

Writes the 256-byte buffer at 5500H back to the current directory sector with a deleted-data address mark, the mark LDOS uses for directory sectors, then verifies it. Any controller error falls through to the @ERROR path. The cylinder is in Register D and the sector in Register E from the caller.

5356H - Read Directory Sector

Reads one sector into the 256-byte buffer at 5500H. The read status 06H, the deleted-data mark that flags a directory sector, is accepted as success alongside a clean read; any other error falls through to the @ERROR path. The cylinder is in Register D and the sector in Register E from the caller.

5362H - Error Display via @ERROR

Common error exit for the disk primitives and the illegal-drive stub. It sets the return-to-caller and message-only option bits, calls the resident @ERROR service to display the system message for the code in Register A, then loads the error return code and exits.

5369H - Message Error Stubs

Three entry points that each load the address of a plain-text error message into Register Pair HL and converge on a single @LOGOT display call. The entries overlap: a single DD byte sits between each 3-byte LD HL, so that when execution falls through from one entry the DD prefixes the following LD HL into a harmless LD IX, preserving the message address already in Register Pair HL.

537DH - Illegal-Drive Error Stub

Reached when the command line lacks a colon, names a drive above 7, or names an unavailable drive. It loads error code 20H (32, illegal drive number) and joins the @ERROR display path.

5381H - Sign-On Message

The banner displayed at start-up through @DSPLY (4467H) at 520BH. The text is terminated by a line feed and carriage return.

53E4H - Conversion-Complete Message

Displayed through @LOGOT (447BH) at 52F4H. The leading five blanks are overwritten by the right-justified file count that the formatter at 5309H builds, leaving the sixth blank as a separator.

540FH - Abort Message

Displayed through @LOGOT (447BH) at 5374H when the operator presses BREAK during conversion (entry 5371H).

5428H - System-Disk Message

Displayed through @LOGOT (447BH) at 5374H when the system-disk gate rejects the pack (entry 5369H).

545BH - Write-Protected Message

Displayed through @LOGOT (447BH) at 5374H when @CKDRV reports the pack write-protected (entry 536DH).

5472H - File-Conversion Counter

The 16-bit running count of directory entries converted. It is initialised to zero in the load image, incremented at 52BAH for each file, and formatted into the completion message at 52E9H.