Acorn ADFS 1.30

Claim the Tube for a data transfer if a Tube is present. Copies the 4-byte transfer address from the control block to workspace and sets the Tube-in-use flag.

Release the Tube after a data transfer if it was claimed. Checks zp_adfs_flags bit 6 and clears it after release.

Read the SCSI status register, waiting for the value to settle. Reads the status twice and loops until consecutive reads match. Also stores result in zp_scsi_status.

Select a SCSI device on the bus and begin the command phase. Asserts the target's SCSI ID on the data bus and waits for the BSY signal to be asserted by the target.

Set the retry counter to the default value (16).

Execute a disc operation using the control block pointed to by X (low) and Y (high). Handles both hard drive (SCSI) and floppy disc operations with retry logic.

Execute a disc operation via the SCSI hard drive interface. Sends the SCSI command bytes from the control block at (&B0), performs data transfer (direct or via Tube), and reads the SCSI status and message phases.

Falls back to floppy if drive bit 7 is set.

Release the Tube, then read the SCSI status and message bytes to determine the outcome of the command.

Transfer complete 256-byte sectors between SCSI bus and memory (direct or via Tube). Optimised inner loop with no per-byte SCSI REQ polling.

Disable interrupts then call the Tube host code at &0406 to initiate a data transfer.

Call the Tube host code at &0406 to initiate a data transfer. Followed by a delay for Tube synchronisation.

Send a SCSI Request Sense command (opcode 3) to retrieve extended error information after a failed operation. Stores the 4-byte sense data in the error workspace.

Execute a disc command using the control block at &1015. Generates a BRK error if the command fails.

Execute disc command via command_exec_xy. On error, generate a BRK (never returns). On success, restore saved drive and return.

Generate a BRK error from the disc error code in A. Never returns to caller.

Wait for SCSI REQ, then write byte A to the SCSI data bus. Returns only on success; generates BRK on error.

If zp_flags bit 0 (ensuring) is set, loop until it clears. This prevents disc operations during file ensure operations.

Poll the SCSI status register until the REQ bit is asserted, indicating the target is ready for the next bus phase. Preserves A; N and V flags reflect SCSI bus phase.

Wait for SCSI REQ then write A to the SCSI data register. May not return if MSG phase detected (unwinds call stack to command_done).

Save the current drive state, reload FSM and directory, then generate a BRK error. The inline error number and message string follow the JSR instruction.

Reload the free space map and current directory from disc, then generate a BRK error. Used after operations that may have left the in-memory copies inconsistent.

Generate a BRK error from the disc error code without appending the drive:sector suffix.

Generate a BRK error from the inline error data following the JSR. X controls whether the drive:sector suffix is appended. Never returns.

Reversed string constants used when building error messages. str_at contains ': ta ' (reversed ' at :') appended to disc error messages, and str_on_channel contains ' lennahc no ' (reversed ' on channel') for channel-specific errors.

Write the byte in A as two ASCII hex digits into the error block at the current position Y.

Convert a 4-bit value in A to an ASCII hex character ('0'-'9' or 'A'-'F'). The low nibble of A is used.

Write the byte in A as up to three decimal digits into the error block at the current position Y, suppressing leading zeros.

Set flags to indicate that the in-memory free space map and directory buffer may be stale and need reloading from disc.

CR-terminated command abbreviation strings passed to OSCLI: str_exec_abbrev = 'E.' (*EXEC), str_spool_abbrev = 'SP.' (*SPOOL). Also includes str_yes (reversed 'YES' + CR for *DESTROY confirmation) and str_hugo (NUL + 'Hugo' directory identity string).

Call OSBYTE with Y=&FF and X=0 to read the current value of the variable specified in A.

Call OSCLI with the command string address in X (low byte).

Return the disc space occupied by the object at wksp_object_sector (3 bytes) with size at &1037-&1039 (3 bytes) back to the free space map. Searches for the correct position in the sorted FSM and merges with adjacent free entries where possible.

Copy the object sector address and add the released block size to an existing FSM length entry, merging adjacent free regions.

Check for room in the FSM. If full, raise Map full error. Otherwise shift entries up and insert the new entry at the correct sorted position.

Walk the FSM entries accumulating the 3-byte length of each free extent into workspace &105D-&105F.

Find the best-fit free entry for the requested size at &103D-&103F. Generates Disc full or Compaction required errors if allocation is not possible.