Acorn ADFS 1.30 Memory Map

← Acorn ADFS

Addresses outside the ROM used by Acorn ADFS 1.30 at run time — zero-page workspace, RAM buffers, and memory-mapped I/O. For the ROM code itself (&8000–&BFFF), see the disassembly listing.

WD1770 floppy driver workspace (&A0–&A6)

Address	Name	Access	Description
`&00A0`	`zp_floppy_error`	R/W	WD1770 floppy driver: result / error code from the last disc operation.
`&00A1`	`zp_floppy_control`	R/W	WD1770 floppy driver: control flags for the current operation (read vs write direction, etc.).
`&00A2`	`zp_floppy_state`	R/W	WD1770 floppy driver: transfer state-machine flags, rotated through as the operation proceeds.
`&00A3`	`zp_floppy_track`	R/W	WD1770 floppy driver: target track for the current operation.
`&00A4`	`zp_floppy_sector`	R/W	WD1770 floppy driver: target sector for the current operation.
`&00A5`	`zp_floppy_track_num`	R/W	WD1770 floppy driver: physical track number, adjusted for the selected head / side.
`&00A6`	`zp_floppy_dest_page`	R/W	WD1770 floppy driver: high byte of the host transfer address (destination page).

Filing-system scratch space (&B0–&BF)

Address	Name	Access	Description
`&00B0`	`zp_ctrl_blk_lo`	R/W	Pointer to the current OSWORD &72 disc-access control block, low byte.
`&00B1`	`zp_ctrl_blk_hi`	R/W	Pointer to the current OSWORD &72 disc-access control block, high byte.
`&00B2`	`zp_mem_ptr_lo`	R/W	Pointer to the host memory address for the current data transfer, low byte.
`&00B3`	`zp_mem_ptr_hi`	R/W	Pointer to the host memory address for the current data transfer, high byte.
`&00B4`	`zp_text_ptr_lo`	R/W	Pointer to the command / text string being parsed, low byte.
`&00B5`	`zp_text_ptr_hi`	R/W	Pointer to the command / text string being parsed, high byte.
`&00B6`	`zp_entry_ptr_lo`	R/W	Pointer to the current directory entry being scanned in the directory buffer, low byte.
`&00B7`	`zp_entry_ptr_hi`	R/W	Pointer to the current directory entry being scanned in the directory buffer, high byte.
`&00B8`	`zp_osfile_ptr_lo`	R/W	Pointer to the OSFILE control block, low byte.
`&00B9`	`zp_osfile_ptr_hi`	R/W	Pointer to the OSFILE control block, high byte.
`&00BA`	`zp_wksp_ptr_lo`	R/W	Saved pointer into ADFS workspace, low byte.
`&00BB`	`zp_wksp_ptr_hi`	W	Saved pointer into ADFS workspace, high byte.
`&00BC`	`zp_buf_src_lo`	R/W	Source pointer for buffer copies, low byte.
`&00BD`	`zp_buf_src_hi`	R/W	Source pointer for buffer copies, high byte.
`&00BE`	`zp_buf_dest_lo`	R/W	Destination pointer for buffer copies, low byte.
`&00BF`	`zp_buf_dest_hi`	R/W	Destination pointer for buffer copies, high byte.

Filing-system workspace (&C0–&CF)

Address	Name	Access	Description
`&00C0`	`zp_name_ptr_lo`	R/W	Pointer to the filename being matched, low byte.
`&00C1`	`zp_name_ptr_hi`	R/W	Pointer to the filename being matched, high byte.
`&00C2`	`zp_save_y`	R/W	Scratch save slot for the Y register (also reused to hold a file handle).
`&00C3`	`zp_save_x`	R/W	Scratch save slot for the X register (zero-page pointer base).
`&00C4`	`zp_osfind_y`	R/W	Saved Y register across OSFIND processing.
`&00C5`	`zp_osfind_x`	R/W	Saved X register across OSFIND processing.
`&00C6`	`zp_gspb_ptr_lo`	R/W	Pointer to the OSGBPB control block, low byte. The free-space-map compaction code at &A069 reuses this location as a scratch map index.
`&00C7`	`zp_gspb_ptr_hi`	R/W	Pointer to the OSGBPB control block, high byte.
`&00C8`	`zp_temp_ptr`	R/W	Temporary 4-byte pointer (byte 0) used for disc-sector address arithmetic, e.g. adding or subtracting a PTR offset.
`&00C9`	`zp_temp_ptr_1`	R	Temporary 4-byte pointer, byte 1.
`&00CA`	`zp_temp_ptr_2`	R	Temporary 4-byte pointer, byte 2.
`&00CB`	`zp_temp_ptr_3`	R	Temporary 4-byte pointer, byte 3.
`&00CC`	`zp_scsi_status`	R/W	Holds a SCSI status byte read back from the host adapter while waiting for the bus to settle.
`&00CD`	`zp_adfs_flags`	R/W	Primary ADFS state flags, the most heavily consulted flag byte. Bit 6 = Tube in use; also records Tube presence and other per-operation conditions.
`&00CE`	`zp_retry_count`	R/W	Retry counter for disc operations, decremented on each failed attempt.
`&00CF`	`zp_channel_offset`	R/W	Index of the current open-file channel within the channel tables.

MOS zero-page locations (&EF–&FF)

Address	Name	Access	Description
`&00EF`	`zp_osbyte_last_a`	R	MOS scratch: A on entry to the last OSBYTE / OSWORD. ADFS reads the OSWORD routine number here when dispatching OSWORD &72.
`&00F0`	`zp_osword_pb_ptr`	R/W	MOS scratch (X on the last OSBYTE / OSWORD): pointer to the OSWORD parameter block, low byte. ADFS reads the disc-access control-block address here.
`&00F1`	`zp_osword_pb_ptr_hi`	R	MOS scratch (Y on the last OSBYTE / OSWORD): pointer to the OSWORD parameter block, high byte.
`&00F2–&00F3`	`os_text_ptr`	R	MOS command-line text pointer (&F2/&F3). ADFS reads through it to fetch each character of a *command tail.
`&00F4`	`romsel_copy`	R/W	MOS RAM copy of the paged-ROM select latch. ADFS reads it to discover its own ROM bank number.
`&00F6–&00F7`	`osrdsc_ptr`	R/W	MOS address pointer (&F6/&F7) used with paged-ROM / OSRDSC access.
`&00FF`	`zp_escape_flag`	R	MOS Escape flag (bit 7 set when an Escape is pending); ADFS polls it during long operations.

MOS vector table (page 2)

Address	Name	Access	Description
`&0212–&0213`	`filev`	W	MOS FILEV vector (OSFILE). ADFS points it at its own OSFILE handler when the filing system is selected.
`&0214–&0215`	`argsv`	W	MOS ARGSV vector (OSARGS), claimed by ADFS on selection.
`&0216–&0217`	`bgetv`	W	MOS BGETV vector (OSBGET), claimed by ADFS on selection.
`&0218–&0219`	`bputv`	W	MOS BPUTV vector (OSBPUT), claimed by ADFS on selection.
`&021A–&021B`	`gbpbv`	W	MOS GBPBV vector (OSGBPB), claimed by ADFS on selection.
`&021C–&021D`	`findv`	W	MOS FINDV vector (OSFIND), claimed by ADFS on selection.
`&021E–&021F`	`fscv`	R/W	MOS FSCV vector (filing-system control). ADFS claims it on selection and the MOS calls through it for *commands, file-system selection and similar control operations.
`&028D`	`last_break_type`	R	MOS last-break-type flag (0=soft, 1=power-on, 2=hard). ADFS reads it during initialisation to decide how much state to rebuild.

NMI handler and workspace (&0D00–&0D5F)

Address	Name	Access	Description
`&0D0A`	`nmi_rw_code`	W	Relocated NMI transfer handler. ADFS copies its sector read/write routine into the page-&0D NMI workspace and patches it at runtime; this is the routine's working area.
`&0D0B`	`nmi_write_addr_lo`	R/W	Patch site in the NMI handler: host buffer address for sector WRITES, low byte.
`&0D0C`	`nmi_write_addr_hi`	R/W	Patch site in the NMI handler: host buffer address for sector WRITES, high byte.
`&0D0E`	`nmi_read_addr_lo`	R/W	Patch site in the NMI handler: host buffer address for sector READS, low byte.
`&0D0F`	`nmi_read_addr_hi`	R/W	Patch site in the NMI handler: host buffer address for sector READS, high byte.
`&0D56`	`nmi_precomp_mask`	R/W	NMI workspace: write precompensation mask (set from keyboard link 4); ORed into WD1770 write commands to enable precompensation.
`&0D57`	`nmi_tracks_remaining`	R/W	NMI workspace: number of whole tracks still to transfer.
`&0D58`	`nmi_secs_this_track`	R/W	NMI workspace: sectors to transfer on the current track.
`&0D59`	`nmi_secs_last_track`	R/W	NMI workspace: sectors to transfer on the final track.
`&0D5A`	`nmi_sec_position`	R/W	NMI workspace: current sector position within the transfer.
`&0D5C`	`nmi_step_rate`	R/W	NMI workspace: stepping-rate mask, a copy of wksp_fdc_cmd_step (&10E8, set from keyboard link 3); ORed into WD1770 Type I seek/step/restore commands.
`&0D5D`	`nmi_adfs_flags`	R/W	NMI workspace: copy of the ADFS flags consulted by the NMI handler.
`&0D5E`	`nmi_drive_ctrl`	R/W	NMI workspace: drive-control byte for the current transfer.
`&0D5F`	`nmi_completion`	W	NMI workspace: completion flag the handler sets when the transfer finishes.

Sideways-ROM private workspace table (&0DF0–&0DFF)

Address	Name	Access	Description
`&0DF0`	`rom_wksp_table`	R/W	Base of the sideways-ROM private workspace table (&0DF0-&0DFF, one byte per ROM bank holding the high byte of that ROM's private RAM). ADFS reads and updates its own bank's entry.

Free space map image (&0E00–&0FFF)

Address	Name	Access	Description
`&0E00`	`fsm_sector_0` index region &0DFA–&0E03	R/W	Free space map sector 0 (&0E00-&0EFF), the RAM image of on-disc sector 0. Holds the START sector address of each free-space fragment, 3 bytes per fragment, lowest first.
`&0EFA`	`fsm_s0_reserved`	R	Reserved byte in FSM sector 0, just below the total-disc-size field. The compaction also reaches it as fsm_sector_1-6 (the notional entry before the first length entry).
`&0EFB`	`fsm_s0_pre_disc_size`	R	Byte just below the total-disc-size field in FSM sector 0; read by the Y-indexed loop that fetches the size.
`&0EFC`	`fsm_s0_disc_size_lo`	R/W	Total number of sectors on the disc (3-byte little-endian), low byte, in FSM sector 0.
`&0EFD`	`fsm_s0_disc_size_mid`	R/W	Total number of sectors on the disc, middle byte.
`&0EFE`	`fsm_s0_disc_size_hi`	R	Total number of sectors on the disc, high byte.
`&0EFF`	`fsm_s0_checksum`	R/W	Checksum byte of FSM sector 0 (validates the free-space start-address map).
`&0F00`	`fsm_sector_1` index region &0F00–&0F03	R/W	Free space map sector 1 (&0F00-&0FFF), the RAM image of on-disc sector 1. Holds the LENGTH in sectors of each free-space fragment, 3 bytes each, paired by index with the start addresses in sector 0.
`&0FFB`	`fsm_s1_disc_id_lo`	R/W	Disc identifier (random 16-bit value assigned at format), low byte, in FSM sector 1.
`&0FFC`	`fsm_s1_disc_id_hi`	R	Disc identifier, high byte.
`&0FFD`	`fsm_s1_boot_option`	R/W	Boot option (*OPT 4 value, 0-3) stored in FSM sector 1.
`&0FFE`	`fsm_s1_end_of_list_ptr`	R/W	Pointer to the end of the free-space list: the number of free-space fragments times 3. Zero means the disc is full.
`&0FFF`	`fsm_s1_checksum`	R/W	Checksum byte of FSM sector 1 (validates the free-space length map and disc parameters).

ADFS private workspace (&1000–&11FF)

Address	Name	Access	Description
`&1000`	`wksp`	R/W	Base of ADFS's private workspace (&1000-&11FF); holds the default retry count.
`&1001`	`wksp_buf_sec_lo`	R/W	Sector address of the data currently in the sector buffer, low byte (mid/high at &1002/&1003).
`&1002`	`wksp_buf_sec_mid`	R/W
`&1003`	`wksp_buf_sec_hi`	R/W
`&1004`	`wksp_buf_flag`	R/W	Sector-buffer state flag.
`&1008`	`wksp_buf_flag_1`	W
`&100C`	`wksp_buf_flag_2`	W
`&1010`	`wksp_osword_block`	W	OSWORD parameter block used to issue low-level disc operations.
`&1011`	`wksp_entry_calc_base`	R
`&1014`	`wksp_disc_op_block`	W	Low-level disc-operation control block: the result, transfer address, command, sector, count and control fields follow.
`&1015`	`wksp_disc_op_result`	R/W	Disc-operation result / status byte.
`&1016`	`wksp_disc_op_mem_addr`	R/W	Host transfer address for the disc operation, byte 0 (4-byte address &1016-&1019).
`&1017`	`wksp_disc_op_mem_addr_1`	R/W
`&1018`	`wksp_disc_op_mem_addr_2`	R/W
`&1019`	`wksp_disc_op_mem_addr_3`	R/W
`&101A`	`wksp_disc_op_command`	R/W	Disc-operation command byte (read / write / verify, etc.).
`&101B`	`wksp_disc_op_sector`	R/W	Target sector for the disc operation, byte 0 (3-byte sector &101B-&101D).
`&101C`	`wksp_disc_op_sector_mid`	R/W
`&101D`	`wksp_disc_op_sector_lo`	R/W
`&101E`	`wksp_disc_op_sector_count`	R/W	Number of sectors to transfer in the disc operation.
`&101F`	`wksp_disc_op_control`	W	Disc-operation control byte.
`&1020`	`wksp_disc_op_transfer_len`	R/W	Partial-transfer byte count for the disc operation (4 bytes).
`&1021`	`wksp_disc_op_xfer_len_1`	R/W
`&1022`	`wksp_disc_op_xfer_len_2`	R/W
`&1023`	`wksp_disc_op_xfer_len_3`	R/W
`&1024`	`wksp_entry_size_base`	W	Scratch for an object's sector count during directory-entry processing.
`&1026`	`wksp_tube_transfer_addr`	W	Tube transfer address for the current operation (4 bytes), when data is moving via the Tube.
`&1027`	`wksp_tube_transfer_addr_1`	R/W
`&1028`	`wksp_tube_xfer_addr_2`	R/W
`&1029`	`wksp_tube_xfer_addr_3`	R/W
`&102A`	`wksp_csd_drive_temp`	R/W	Temporary current-selected-directory (CSD) drive number.
`&102B`	`wksp_csd_sector_temp`	R/W	Temporary CSD sector.
`&102C`	`wksp_csd_drive_sector`	R/W	CSD drive+sector working copy.
`&102D`	`wksp_csd_drive_sector_mid`	R/W
`&102E`	`wksp_alt_sector_hi`	R/W
`&102F`	`wksp_saved_drive`	R/W	Saved drive number.
`&1030`	`wksp_temp_sector`	R/W	Temporary sector store.
`&1033`	`wksp_last_access_drive`	R/W	Drive of the most recent disc access.
`&1034`	`wksp_object_sector`	R/W	Sector address of the object (file or directory) being processed, low byte (3 bytes).
`&1035`	`wksp_object_sector_mid`	R/W
`&1036`	`wksp_object_sector_hi`	R/W
`&1037`	`wksp_object_size`	R/W	Size in bytes of the object being processed, low byte (3 bytes).
`&1038`	`wksp_object_size_mid`	R/W
`&1039`	`wksp_object_size_hi`	R/W
`&103A`	`wksp_alloc_sector`	R/W	Start sector of a newly allocated region.
`&103B`	`wksp_saved_count`	R/W	Saved sector / entry count.
`&103C`	`wksp_saved_count_1`	R/W
`&103D`	`wksp_alloc_size`	R/W	Size of a newly allocated region, low byte (3 bytes).
`&103E`	`wksp_alloc_size_mid`	W
`&103F`	`wksp_alloc_size_hi`	R/W
`&1040`	`wksp_osfile_block`	R/W	OSFILE control block built and parsed here: filename pointer, load/exec/start/end addresses and attributes.
`&1041`	`wksp_osfile_block_1`	R/W
`&1042`	`wksp_osfile_load_addr`	R/W	OSFILE load address (4 bytes).
`&1043`	`wksp_osfile_load_addr_1`	R/W
`&1046`	`wksp_osfile_exec_addr`	W	OSFILE execution address (4 bytes).
`&1047`	`wksp_osfile_exec_addr_1`	W
`&1048`	`wksp_osfile_exec_addr_2`	W
`&1049`	`wksp_osfile_exec_addr_3`	W
`&104A`	`wksp_osfile_start_addr`	W	OSFILE start address / length, byte 0 (4 bytes).
`&104B`	`wksp_osfile_start_addr_1`	W
`&104C`	`wksp_osfile_start_addr_2`	W
`&104D`	`wksp_osfile_start_addr_3`	W
`&104F`	`wksp_osfile_end_addr_1`	R/W
`&1050`	`wksp_osfile_end_addr_2`	W
`&1052`	`wksp_osfile_attr`	R/W	Object attributes (access bits) in the OSFILE block.
`&1053`	`wksp_osfile_attr_1`	W
`&1054`	`wksp_osfile_attr_2`	W
`&105D`	`wksp_access_accum`	R/W	Accumulator for summing free space and sizes, low byte (3 bytes).
`&105E`	`wksp_access_accum_1`	W
`&105F`	`wksp_free_space_total`	W	Running total of free space (high byte of the accumulator).
`&1060`	`wksp_compact_start_page`	R/W	Start page of the buffer used during *COMPACT.
`&1061`	`wksp_compact_length`	R/W	Length of data held in the compaction buffer.
`&1062`	`wksp_object_name`	R/W	Name of the object being processed (10 bytes).
`&1063`	`wksp_object_name_1`	W
`&106C`	`wksp_saved_dir_sector`	R/W	Saved directory sector.
`&106F`	`wksp_drive_number`	R/W	Working drive number (e.g. for *MOUNT).
`&1070`	`wksp_new_parent_sector`	R/W	New parent-directory sector for a created or moved object.
`&1073`	`wksp_dest_drive`	R	Destination drive for COPY / RENAME.
`&1074`	`wksp_dest_name`	R/W	Destination object name (for COPY / RENAME).
`&107E`	`wksp_dest_filename_end`	W	End marker of the destination filename.
`&107F`	`wksp_copy_name_ptr`	W	Pointer to the source name during *COPY, low byte (high at &1080).
`&1080`	`wksp_copy_name_ptr_hi`	W
`&1089`	`wksp_copy_osfile_params`	R/W	Saved source OSFILE parameters during *COPY.
`&108C`	`wksp_copy_osfile_exec`	R/W
`&108D`	`wksp_copy_dest_params`	W	Destination OSFILE parameters during *COPY.
`&1091`	`wksp_filename_save`	R/W	Saved filename pointer, low byte (high at &1092).
`&1092`	`wksp_filename_save_hi`	R/W
`&1093`	`wksp_entry_save`	R/W	Saved directory-entry pointer, low byte (high at &1094).
`&1094`	`wksp_entry_save_hi`	R/W
`&1095`	`wksp_osgbpb_end_ptr`	R/W	OSGBPB working end pointer.
`&1096`	`wksp_osgbpb_sector_lo`	R/W	OSGBPB working sector, low byte (3 bytes).
`&1097`	`wksp_osgbpb_sector_mid`	R/W
`&1098`	`wksp_osgbpb_sector_hi`	R/W
`&109A`	`wksp_new_ptr_lo`	R/W	Newly computed file PTR, low byte (multi-byte).
`&109B`	`wksp_new_ptr_mid`	R/W
`&109C`	`wksp_new_ptr_mid_hi`	R/W
`&109D`	`wksp_new_ptr_hi`	R/W
`&109E`	`wksp_new_ptr_4`	R/W
`&109F`	`wksp_osgbpb_wksp_9f`	R/W
`&10A0`	`wksp_ch_buf_sector`	R/W	Current sector held in the channel buffer.
`&10A1`	`wksp_ch_buf_sector_1`	R/W
`&10A2`	`wksp_copy_read_sector`	R/W	*COPY source (read) sector, byte 0.
`&10A3`	`wksp_copy_read_sector_1`	R/W
`&10A4`	`wksp_copy_read_sector_2`	R/W
`&10A5`	`wksp_copy_write_sector`	R/W	*COPY destination (write) sector, byte 0.
`&10A6`	`wksp_copy_write_sector_1`	R/W
`&10A7`	`wksp_copy_write_sector_2`	R/W
`&10A8`	`wksp_copy_src_sector`	R/W	*COPY source sector working copy.
`&10A9`	`wksp_copy_src_sector_1`	R/W
`&10AA`	`wksp_copy_src_sector_2`	R/W
`&10AB`	`wksp_copy_dest_sector`	R/W	*COPY destination sector working copy.
`&10AC`	`wksp_copy_dest_sector_1`	W
`&10AD`	`wksp_copy_dest_sector_2`	W
`&10B4`	`wksp_osgbpb_func`	R/W	OSGBPB function code (1-8).
`&10B5`	`wksp_osgbpb_mode`	R/W	OSGBPB open mode / extension flag.
`&10B6`	`wksp_osgbpb_start`	R/W	OSGBPB transfer start position.
`&10B7`	`wksp_osgbpb_end`	R/W	OSGBPB transfer end position.
`&10B8`	`wksp_osgbpb_data_addr`	R/W	OSGBPB cumulative data transfer address (4 bytes).
`&10B9`	`wksp_osgbpb_data_addr_1`	R/W
`&10BA`	`wksp_osgbpb_data_addr_2`	R/W
`&10BB`	`wksp_osgbpb_data_addr_3`	R/W
`&10BC`	`wksp_osgbpb_wksp_bc`	R/W
`&10BD`	`wksp_osgbpb_byte_count`	R/W	OSGBPB byte count for the transfer.
`&10BE`	`wksp_osgbpb_name_offset`	R/W	OSGBPB offset into the name being read or written.
`&10BF`	`wksp_saved_drive_2`	R/W	Second saved drive number.
`&10C0`	`wksp_search_flag`	R/W	Directory-search state flag.
`&10C1`	`wksp_workspace_checksum`	R/W	Checksum of critical workspace, validated to detect corruption.
`&10C2`	`wksp_drive_change_mask`	R/W	Bit mask of drives whose media may have changed.
`&10C3`	`wksp_prev_clock`	R/W	Previous clock reading, for elapsed-time comparison.
`&10C8`	`wksp_clock`	R/W	Cached system clock value, byte 0 (5-byte TIME).
`&10C9`	`wksp_clock_1`	R
`&10CA`	`wksp_clock_2`	R
`&10CB`	`wksp_clock_3`	R
`&10CC`	`wksp_clock_4`	R
`&10CD`	`wksp_clock_5`	R/W
`&10CE`	`wksp_error_suppress`	R/W	Flag suppressing error reporting in some code paths.
`&10CF`	`wksp_bput_modified`	R/W	Flag: the current channel buffer was modified by OSBPUT and needs flushing.
`&10D0`	`wksp_err_sector`	R/W	Sector associated with the last disc error, low byte (3 bytes).
`&10D1`	`wksp_err_sector_mid`	W
`&10D2`	`wksp_err_sector_hi`	R/W
`&10D3`	`wksp_err_code`	R/W	Last disc error code.
`&10D4`	`wksp_err_handle`	R/W	File handle associated with the last error.
`&10D5`	`wksp_cur_channel`	R/W	Current open-file channel number.
`&10D6`	`wksp_cmd_tail`	R/W	Pointer to the *command tail, low byte (high at &10D7).
`&10D7`	`wksp_cmd_tail_hi`	R/W
`&10D8`	`wksp_compaction_reported`	R/W	Flag: a compaction-needed condition has already been reported.
`&10E0`	`wksp_fdc_xfer_mode`	R/W	WD1770 transfer direction / mode for the current floppy operation.
`&10E1`	`wksp_nmi_owner`	R/W	Owner of the NMI, claimed during disc transfers and released afterwards.
`&10E2`	`wksp_format_page`	R/W	Page counter / buffer during *FORMAT.
`&10E3`	`wksp_err_number`	R/W	Working error number.
`&10E4`	`wksp_fdc_head_state`	R/W	WD1770 head / load state.
`&10E5`	`wksp_fdc_track_0`	R/W	Last known track for drive 0 (head-position cache).
`&10E6`	`wksp_fdc_track_1`	R/W	Last known track for drive 1 (head-position cache).
`&10E7`	`wksp_stack_save`	R/W	Saved stack pointer for error recovery.
`&10E8`	`wksp_fdc_cmd_step`	R/W	WD1770 Type I stepping-rate setting (from keyboard link 3); copied into nmi_step_rate for the NMI transfer.
`&1100`	`wksp_csd_name`	R/W	Name of the current selected directory (CSD), 10 characters.
`&110A`	`wksp_lib_name`	W	Name of the library directory, 10 characters.
`&1113`	`wksp_csd_sector`	R/W	CSD sector marker / validity byte.
`&1114`	`wksp_csd_sector_lo`	R/W	Sector of the current selected directory, low byte (3 bytes).
`&1115`	`wksp_csd_sector_mid`	R/W
`&1116`	`wksp_csd_sector_hi`	R/W
`&1117`	`wksp_current_drive`	R/W	Current default drive number.
`&1118`	`wksp_lib_sector`	R/W	Library directory sector marker / validity byte.
`&1119`	`wksp_lib_sector_lo`	R	Sector of the library directory, low byte (3 bytes).
`&111A`	`wksp_lib_sector_mid`	R/W
`&111B`	`wksp_lib_sector_hi`	R/W
`&111C`	`wksp_prev_dir_sector`	R/W	Previous directory (^) sector marker / validity byte.
`&111D`	`wksp_prev_dir_sector_lo`	W	Sector of the previous directory, low byte (3 bytes).
`&111E`	`wksp_prev_dir_sector_mid`	W
`&111F`	`wksp_prev_dir_sector_hi`	R/W
`&1120`	`wksp_flags_save`	R/W	Saved status flags.
`&1121`	`wksp_disc_id_lo`	R/W	Cached disc identifier, low byte (high at &1122).
`&1122`	`wksp_disc_id_hi`	R/W
`&1131`	`wksp_scsi_status`	R/W	Combined SCSI status from the last hard-disc operation.
`&1132`	`wksp_exec_handle`	R/W	File handle of the current *EXEC file.
`&1133`	`wksp_current_drive_hi`	R/W	Current drive / LUN combined byte for the hard disc.
`&1134`	`wksp_ch_ext_h`	R/W	Channel table - file EXTENT (length), high byte. One byte per open channel.
`&113E`	`wksp_ch_ext_mh`	R/W	Channel table - file EXTENT, mid-high byte (per channel).
`&1148`	`wksp_ch_ext_ml`	R/W	Channel table - file EXTENT, mid-low byte (per channel).
`&1152`	`wksp_ch_ext_l`	R/W	Channel table - file EXTENT, low byte (per channel).
`&115C`	`wksp_ch_ptr_h`	R/W	Channel table - file PTR (sequential position), high byte (per channel).
`&1166`	`wksp_ch_ptr_mh`	R/W	Channel table - file PTR, mid-high byte (per channel).
`&1170`	`wksp_ch_ptr_ml`	R/W	Channel table - file PTR, mid-low byte (per channel).
`&117A`	`wksp_ch_ptr_l`	R/W	Channel table - file PTR, low byte (per channel).
`&1183`	`wksp_ch_alloc_pad`	R	Channel table - allocated size, padding / first byte (per channel).
`&1184`	`wksp_ch_alloc_h`	R/W	Channel table - allocated size, high byte (per channel).
`&118E`	`wksp_ch_alloc_mh`	R/W	Channel table - allocated size, mid-high byte (per channel).
`&1198`	`wksp_ch_alloc_ml`	R/W	Channel table - allocated size, mid-low byte (per channel).
`&11A2`	`wksp_ch_alloc_l`	R/W	Channel table - allocated size, low byte (per channel).
`&11AC`	`wksp_ch_flags`	R/W	Channel table - per-channel flags (open mode, modified, etc.).
`&11B6`	`wksp_ch_start_sec_h`	R/W	Channel table - file's start sector, high byte (per channel).
`&11C0`	`wksp_ch_start_sec_mh`	R/W	Channel table - file's start sector, mid-high byte (per channel).
`&11CA`	`wksp_ch_start_sec_ml`	R/W	Channel table - file's start sector, mid-low byte (per channel).
`&11D4`	`wksp_ch_dir_sec_h`	R/W	Channel table - parent-directory sector, high byte (per channel).
`&11DE`	`wksp_ch_dir_sec_mh`	R/W	Channel table - parent-directory sector, mid-high byte (per channel).
`&11E8`	`wksp_ch_dir_sec_ml`	R/W	Channel table - parent-directory sector, mid-low byte (per channel).
`&11F2`	`wksp_ch_seq_num`	R/W	Channel table - directory sequence number when the file was opened, for staleness checks (per channel).

Directory buffer (&1200–&16FF)

Address	Name	Access	Description
`&1200`	`dir_buffer`	R/W	Directory buffer (&1200-&16FF, five sectors). Holds the currently loaded directory - a header, up to 47 26-byte entries, and a footer. This is the start of the header.
`&1205`	`dir_first_entry`	R	First 26-byte directory entry (offset &05 into the buffer, just past the header).
`&16B1`	`dir_last_entry_area`	R	End of the directory entry area; the entry list is searched up to this limit when looking for a free slot.
`&16CC`	`dir_name`	R/W	Directory's own name, stored in the footer.
`&16D6`	`dir_parent_sector`	W	Sector address of this directory's parent (3 bytes), stored in the footer.
`&16D9`	`dir_title`	R/W	Directory title string, stored in the footer.
`&16FA`	`dir_master_sequence`	R/W	Master sequence number in the footer, bumped on each change to detect concurrent updates.
`&16FB`	`dir_identity_string`	R/W	Footer identity string ('Hugo'); must match the header's copy to validate the directory.

Random-access buffers (&1700–&1BFF)

Address	Name	Access	Description
`&1700`	`ra_buffer_1`	W	General-purpose buffer page 1 (&1700). Used for sector read-ahead and as scratch during directory and free-space operations; also reused as a second directory header.
`&1800`	`ra_buffer_2`	W	General-purpose buffer page 2 (&1800).
`&1900`	`ra_buffer_3`	W	General-purpose buffer page 3 (&1900).
`&1A00`	`ra_buffer_4`	W	General-purpose buffer page 4 (&1A00).
`&1B00`	`ra_buffer_5`	W	General-purpose buffer page 5 (&1B00); also holds a second directory image when an operation works on two directories at once.
`&1BCC`	`dir2_name`	W	Footer name of the second directory held in the &1B00 buffer (used by operations that touch two directories, such as *COPY or rename across directories).
`&1BD6`	`dir2_parent_sector`	W	Parent-directory sector of the second directory, in its footer.
`&1BD9`	`dir2_title`	W	Title of the second directory, in its footer.
`&1BFA`	`dir2_master_sequence`	W	Master sequence number of the second directory, in its footer.

Memory-mapped I/O

Address	Name	Access	Description
`&FC40`	`scsi_data`	R/W	SCSI data-bus register. Each read or write transfers one byte to or from the Adaptec ACB-4000 controller during the data, status, message and command phases of the SCSI handshake.
`&FC41`	`scsi_status`	R	SCSI bus-status register. Reflects the control-bus phase lines (BSY, REQ, C/D, I/O, MSG) so the driver can step through the SCSI handshake.
`&FC42`	`scsi_select`	W	SCSI select register. A write asserts SEL to start the selection phase and address the controller.
`&FC43`	`scsi_irq_enable`	W	SCSI interrupt-enable register. Controls whether the host adapter raises IRQ on a SCSI data request.
`&FE30`	`romsel`	W	Paged-ROM select latch. ADFS writes a bank number here to page in sideways ROM 0 (and to restore the previous bank afterwards) when reaching code or data in another bank.
`&FE44`	`system_via_t1c_l`	R	System VIA Timer 1 counter, low byte. ADFS reads the free-running counter to seed the low byte of a newly formatted disc's identifier; the read also clears the Timer 1 interrupt flag.
`&FE80`	`fdc_1770_drive_control`	R/W	WD1770 drive-control latch (external to the FDC). Selects the drive, side and density, and drives the controller reset line.
`&FE84`	`fdc_1770_command_or_status`	R/W	WD1770 command register (write) / status register (read).
`&FE85`	`fdc_1770_track`	R/W	WD1770 track register — current track number under the head.
`&FE86`	`fdc_1770_sector`	R/W	WD1770 sector register — target sector for the next read or write.
`&FE87`	`fdc_1770_data`	R/W	WD1770 data register — byte transferred to or from the disc.
`&FEE5`	`tube_data_register_3`	R/W	Tube FIFO register 3 data port. When a second processor is attached, ADFS streams file data through Tube R3 rather than moving it through host memory.

Index bases

Addresses used only as an indexing base — the operand names a base and the byte actually touched is base + X (or + Y), where the index register is a caller-supplied offset, never zero. The literal byte at the base address is never read or written, so these are documented here rather than on the memory map: they are bases, not locations the ROM owns.

Zero Page

Base	Name	Description
`&0000`	`zp_user_ptr_0`	Caller's zero-page pointer, byte 0. ADFS copies a 32-bit address / file PTR to and from this X-indexed location (base+0..+3) when servicing transfers, where X is the caller's control-block pointer (never 0).
`&0001`	`zp_user_ptr_1`	Caller's zero-page pointer, byte 1 (X-indexed base+1).
`&0002`	`zp_user_ptr_2`	Caller's zero-page pointer, byte 2 (X-indexed base+2).
`&0003`	`zp_user_ptr_3`	Caller's zero-page pointer, byte 3 (X-indexed base+3).

ADFS private workspace (&1000–&11FF)

Base	Name	Description
`&100D`	`wksp_entry_field_base`	Index base for the directory-entry field copy: an entry's load/exec/length/attribute fields are read/written as base+Y with Y a field offset (&0A-&15), landing in the disc-op block at &1017-&1022.
`&100E`	`wksp_entry_len_base`	Index base for writing the entry length field (accessed as base+Y with Y a directory-entry field offset >= &12).
`&10FE`	`wksp_alt_csd_sector`	Index base for setting the CSD sector during subdirectory traversal: written as base+Y with Y=&16-&18, landing on wksp_csd_sector at &1114-&1116.