Acorn NFS 3.34B

Parses the character after *NET as '1'-'4', maps to table indices 33-36 via base offset Y=&20, and dispatches via &809F. Characters outside '1'-'4' fall through to return_1 (RTS).

These are internal sub-commands used only by the ROM itself, not user-accessible star commands. The MOS command parser requires a space or terminator after 'NET', so *NET1 typed at the command line does not match; these are reached only via OSCLI calls within the ROM.

*NET1 (&8DB0): read file handle from received packet (net_1_read_handle)

*NET2 (&8DCA): read handle entry from workspace (net_2_read_handle_entry)

*NET3 (&8DE0): close handle / mark as unused (net_3_close_handle)

*NET4 (&8DF3): resume after remote operation (net_4_resume_remote)

Copies command text from (fs_crc_lo) to &0F05+ via copy_filename, prepares an FS command with function code 0, and sends it to the fileserver to request decoding. The server returns a command code indicating what action to take (e.g. code 4=INFO, 7=DIR, 9=LIB, 5=load-as-command). This mechanism allows the fileserver to extend the client's command set without ROM updates. Called from the "I." and catch-all entries in the command match table at &8BD7, and from FSCV 2/3/4 indirectly. If CSD handle is zero (not logged in), returns without sending.

Entered via the extended vector table when the MOS calls FSCV. Stores A/X/Y via save_fscv_args, compares A (function code) against 8, and dispatches codes 0-7 via the shared dispatch table at &8020 with base offset Y=&12 (table indices 19-26). Function codes: 0=*OPT, 1=EOF, 2=*/, 3=unrecognised *, 4=*RUN, 5=*CAT, 6=shutdown, 7=read handles.

Called when the NFS ROM is entered as a language. Although rom_type (&82) does not set the language bit, the MOS enters this point after NFS claims service &FE (Tube post-init). X = reason code (0-4). Dispatches via table indices 14-18 (base offset Y=&0D).

X = command index within caller's group (e.g. service number) Y = base offset into dispatch table (0, &0D, &20, etc.) The loop adds Y+1 to X, so final X = command index + base + 1. Then high and low bytes of (handler-1) are pushed onto the stack, and RTS pops them and jumps to handler_address.

This is a standard 6502 trick: RTS increments the popped address by 1 before jumping, so the table stores (address - 1) to compensate. Multiple callers share one table via different Y base offsets.

Intercepts three special service calls before normal dispatch: &FE: Tube init — explode character definitions (OSBYTE &14, X=6) &FF: Full init — set up WRCHV/RDCHV/BRKV/EVNTV, copy NMI handler code from ROM to RAM pages &04-&06, copy workspace init to &0016-&0076, then fall through to select NFS. &12 with Y=5: Select NFS as active filing system. All other service calls dispatch via dispatch_service (&8127).

Sets up OS vectors for Tube co-processor support: WRCHV = &051C (page 5 — WRCH handler) RDCHV = &04E7 (page 4 — RDCH handler) BRKV = &0016 (workspace — BRK/error handler) EVNTV = &06E8 (page 6 — event handler) Writes &8E to Tube control register (&FEE0). Then copies 3 pages of Tube host code from ROM (tube_code_page4, tube_dispatch_table, tube_code_page6) to RAM (&0400/&0500/&0600), calls tube_post_init (&0414), and copies 97 bytes of workspace init from ROM (nmi_workspace_start) to &0016-&0076.

Dispatches MOS service calls 0-12 via the shared dispatch table. Uses base offset Y=0, so table index = service number + 1. Service numbers >= 13 are ignored (branch to return_2). Called via JSR &809F rather than fall-through, so it returns to &813C to restore saved registers.

Common return path for all dispatched service handlers. Restores rom_svc_num from the stack (pushed by dispatch_service), transfers X (ROM number) to A, then returns via RTS.

Checks byte 4 of (net_rx_ptr): if non-zero, the keyboard was disabled during a remote operation (peek/poke/boot). Clears the flag, re-enables the keyboard via OSBYTE &C9, and sends function &0A to notify completion. Also handles *ROFF and the triple-plus escape sequence (+++), which resets system masks via OSBYTE &CE and returns control to the MOS, providing an escape route when a remote session becomes unresponsive.

Matches the command text against ROM string table entries. Both entries reuse bytes from the ROM header to save space:

  X=8: matches "ROFF" at copyright_string+3 — the suffix
       of "(C)ROFF" → *ROFF (Remote Off,
       end remote session) — jumps to resume_after_remote

  X=1: matches "NET" at &8009 — the ROM title string
       → *NET (select NFS) — falls through to select_nfs

If neither matches, returns with the service call unclaimed.

Reached from service &12 (select FS) with Y=5, or when *NET command selects NFS. Notifies the current FS of shutdown via FSCV A=6 — this triggers the outgoing FS to save its context back to its workspace page, allowing restoration if re-selected later (the FSDIE handoff mechanism). Then sets up the standard OS vector indirections (FILEV through FSCV) to NFS entry points, claims the extended vector table entries, and issues service &0F (vectors claimed) to notify other ROMs. If nfs_temp is zero (auto-boot not inhibited), injects the synthetic command "I .BOOT" through the command decoder to trigger auto-boot login.

Compares characters from (os_text_ptr)+Y against bytes starting at binary_version+X (&8008+X). Input is uppercased via AND &DF. Returns with Z=1 if the ROM string's NUL terminator was reached (match), or Z=0 if a mismatch was found. On match, Y points past the matched text; on return, skips trailing spaces.

Prints the ROM identification string using print_inline.

Loads A=6 (FS shutdown notification) and JMP (FSCV). The FSCV handler's RTS returns to the caller of this routine (JSR/JMP trick saves one level of stack).

Notifies current FS of shutdown via FSCV A=6. Scans keyboard (OSBYTE &7A): if the 'N' key is pressed (matrix address &55), the keypress is forgotten via OSBYTE &78 and auto-boot proceeds. Any other key causes the auto-boot to be declined. If no key is pressed, auto-boot proceeds directly. Falls through to print_station_info, then init_fs_vectors.

Checks if the pressed key (in A) is 'N' (matrix address &55). If not 'N', returns to the MOS without claiming the service call (another ROM may boot instead). If 'N', forgets the keypress via OSBYTE &78 and falls through to print_station_info.

Prints "Econet Station <n>" using the station number from the net receive buffer, then tests ADLC SR2 for the network clock signal — prints " No Clock" if absent. Falls through to init_fs_vectors.

Copies 14 bytes from fs_vector_addrs (&824E) into FILEV-FSCV (&0212), setting all 7 filing system vectors to the extended vector dispatch addresses (&FF1B-&FF2D). Calls setup_rom_ptrs_netv to install the ROM pointer table entries with the actual NFS handler addresses. Also reached directly from select_nfs, bypassing the station display. Falls through to issue_vectors_claimed.

Issues service &0F (vectors claimed) via OSBYTE &8F, then service &0A. If nfs_temp is zero (auto-boot not inhibited), sets up the command string "I .BOOT" at &8246 and jumps to the FSCV 3 unrecognised-command handler (which matches against the command table at &8BD7). The "I." prefix triggers the catch-all entry which forwards the command to the fileserver. Falls through to run_fscv_cmd.

Sets Y to the ROM page high byte (&82) and jumps to fscv_3_star_cmd to execute the command string at (X, Y). X is pre-loaded by the caller with the low byte of the string address. Also used as a data base address by store_rom_ptr_pair for Y-indexed access to the handler address table.

Bytes 0-13: extended vector dispatch addresses, copied to FILEV-FSCV (&0212) by init_fs_vectors. Each 2-byte pair is a dispatch address (&FF1B-&FF2D) that the MOS uses to look up the handler in the ROM pointer table.

Bytes 14-33: handler address pairs read by store_rom_ptr_pair. Each entry has addr_lo, addr_hi, then a padding byte that is overwritten with the current ROM bank number at runtime. The last entry (FSCV) has no padding byte.

Claims pages up to &10 for NMI workspace (&0D), FS state (&0E), and FS command buffer (&0F). If Y >= &10, workspace already allocated — returns unchanged.

Y = next available workspace page on entry. Sets up net_rx_ptr (Y) and nfs_workspace (Y+1) page pointers. On soft break (OSBYTE &FD returns 0): skips FS state init, preserving existing login state, file server selection, and control block configuration — this is why pressing BREAK keeps the user logged in. On power-up/CTRL-BREAK (result non-zero): - Sets FS server station to &FE (FS, the default; no server) - Sets printer server to &EB (PS, the default) - Clears FS handles, OPT byte, message flag, SEQNOS - Initialises all RXCBs with &3F flag (available) In both cases: reads station ID from &FE18 (only valid during reset), calls adlc_init, enables user-level RX (LFLAG=&40).

Reads the ROM pointer table base address via OSBYTE &A8, stores it in osrdsc_ptr (&F6). Sets NETV low byte to &36. Then copies one 3-byte extended vector entry (addr=&9008, rom=current) into the ROM pointer table at offset &36, installing osword_dispatch as the NETV handler.

Called when another filing system (e.g. DFS) is selected. Saves the current NFS context (FSLOCN station number, URD/CSD/LIB handles, OPT byte, etc.) from page &0E into the dynamic workspace backup area. This allows the state to be restored when *NET is re-issued later, without losing the login session. Finally calls OSBYTE &7B (printer driver going dormant) to release the Econet network printer on FS switch.

Loads port &90 (PREPLY) into A, calls init_tx_ctrl_block to set up the TX control block, stores the port and control bytes, then decrements the control flag. Used by send_fs_reply_cmd to prepare for receiving the fileserver's reply.

Copies 12 bytes from tx_ctrl_template (&8335) to &00C0. For the first 2 bytes (Y=0,1), also copies the fileserver station/network from &0E00/&0E01 to &00C2/&00C3. The template sets up: control=&80, port=&99 (FS command port), command data length=&0F, plus padding bytes.

12-byte template copied to &00C0 by init_tx_ctrl. Defines the TX control block for FS commands: control flag, port, station/ network, and data buffer pointers (&0F00-&0FFF). The 4-byte Econet addresses use only the low 2 bytes; upper bytes are &FF.

Alternate entry to prepare_fs_cmd that pushes A, loads &2A into fs_error_ptr, and enters with carry set (SEC). The carry flag is later tested by build_send_fs_cmd to select the byte-stream (BSXMIT) transmission path.

Closes any open *SPOOL and *EXEC files via OSBYTE &77 (FXSPEX), then falls into prepare_fs_cmd with Y=&17 (FCBYE: logoff code). Dispatched from the command match table at &8BD7 for "BYE".

Builds the 5-byte FS protocol header at &0F00: &0F00 HDRREP = reply port (set downstream, typically &90/PREPLY) &0F01 HDRFN = Y parameter (function code) &0F02 HDRURD = URD handle (from &0E02) &0F03 HDRCSD = CSD handle (from &0E03) &0F04 HDRLIB = LIB handle (from &0E04) Command-specific data follows at &0F05 (TXBUF). Also clears V flag. Called before building specific FS commands for transmission.

Sets reply port to &90 (PREPLY) at &0F00, initialises the TX control block, then adjusts TXCB's high pointer (HPTR) to X+5 -- the 5-byte FS header (reply port, function code, URD, CSD, LIB) plus the command data -- so only meaningful bytes are transmitted, conserving Econet bandwidth. If carry is set on entry (DOFSBX byte-stream path), takes the alternate path through econet_tx_retry for direct BSXMIT transmission. Otherwise sets up the TX pointer via setup_tx_ptr_c0 and falls through to send_fs_reply_cmd for reply handling. The carry flag is the sole discriminator between byte-stream and standard FS protocol paths -- set by SEC at the BPUTV/BGETV entry points. On return from WAITFS/BSXMIT, Y=0; INY advances past the command code to read the return code. Error &D6 ("not found", on_entry={"x": "buffer extent (command-specific data bytes)", "y": "function code", "a": "timeout period for FS reply", "c": "0 for standard FS path, 1 for byte-stream (BSXMIT)"}, on_exit={"a": "0 on success", "x": "0 on success, &D6 on not-found", "y": "1 (offset past command code in reply)"}) is detected via ADC #(&100-&D6) with C=0 -- if the return code was exactly &D6, the result wraps to zero (Z=1). This is a branchless comparison returning C=1, A=0 as a soft error that callers can handle, vs hard errors which go through FSERR.

BPUTV enters at &83A3 (CLC; fall through) and BGETV enters at &8486 (SEC; JSR here). The carry flag is preserved via PHP/PLP through the call chain and tested later (BCS) to select byte-stream transmission (BSXMIT) vs normal FS transmission (FSXMIT) -- a control-flow encoding using processor flags to avoid an extra flag variable.

BSXMIT uses handle=0 for print stream transactions (which sidestep the SEQNOS sequence number manipulation) and non-zero handles for file operations. After transmission, the high pointer bytes of the CB are reset to &FF -- "The BGET/PUT byte fix" which prevents stale buffer pointers corrupting subsequent byte-level operations.

The fileserver returns errors as: zero command code + error number + CR-terminated message string. This routine converts the reply buffer in-place to a standard MOS BRK error packet by: 1. Storing the error code at fs_last_error (&0E09) 2. Normalizing error codes below &A8 to &A8 (the standard FS error number), since the MOS error space below &A8 has other meanings 3. Scanning for the CR terminator and replacing it with &00 4. JMPing indirect through (l00c4) to execute the buffer as a BRK instruction — the zero command code serves as the BRK opcode N.B. This relies on the fileserver always returning a zero command code in position 0 of the reply buffer.

Performs a complete FS transaction: transmit then wait for reply. Sets bit 7 of rx_status_flags (mark FS transaction in progress), builds a TX frame from the data at (net_tx_ptr), and transmits it. The system RX flag (LFLAG bit 7) is only set when receiving into the page-zero control block — if RXCBP's high byte is non-zero, setting the system flag would interfere with other RX operations. The timeout counter uses the stack (indexed via TSX) rather than memory to avoid bus conflicts with Econet hardware during the tight polling loop. Handles multi-block replies and checks for escape conditions between blocks.

Two-level escape gating: the MOS escape flag (&FF bit 7) is ANDed with the software enable flag ESCAP. Both must have bit 7 set for escape to fire. ESCAP is set non-zero during data port operations (LOADOP stores the data port &90, serving double duty as both the port number and the escape-enable flag). ESCAP is disabled via LSR in the ENTER routine, which clears bit 7 — PHP/PLP around the LSR preserves the carry flag since ENTER is called from contexts where carry has semantic meaning (e.g., PUTBYT vs BGET distinction). This architecture allows escape between retransmission attempts but prevents interruption during critical FS transactions. If escape fires: acknowledges via OSBYTE &7E, then checks whether the failing handle is the current SPOOL or EXEC handle (OSBYTE &C6/&C7); if so, issues "*SP." or "*E." via OSCLI to gracefully close the channel before raising the error — preventing the system from continuing to spool output to a broken file handle.

Tests MOS escape flag (&FF bit 7). If escape is pending: acknowledges via OSBYTE &7E, writes &3F (deleted marker) into the control block via (net_tx_ptr),Y, and branches to the NLISTN error path. If no escape, returns immediately.

Stores A, X, Y into the filing system workspace. Called at the start of every FS vector handler (FILEV, ARGSV, BGETV, BPUTV, GBPBV, FINDV, FSCV). NFS repurposes CFS/RFS workspace locations: &BD (fs_last_byte_flag) = A (function code / command) &BB (fs_options) = X (control block ptr low) &BC (fs_block_offset) = Y (control block ptr high) &BE/&BF (fs_crc_lo/hi) = X/Y (duplicate for indexed access)

Reads attribute byte at offset &0E from the parameter block, masks to 6 bits, then falls through to the shared bitmask builder. Converts fileserver protection format (5-6 bits) to BBC OSFILE attribute format (8 bits) via the lookup table at &8531. The two formats use different bit layouts for file protection attributes.

Masks A to 5 bits and builds an access bitmask via the lookup table at &8531. Each input bit position maps to a different output bit via the table. The conversion is done by iterating through the source bits and OR-ing in the corresponding destination bits from the table, translating between BBC (8-bit) and fileserver (5-bit) protection formats.

Pops the return address from the stack, prints each byte via OSASCI until a byte with bit 7 set is found, then jumps to that address. The high-bit byte serves as both the string terminator and the opcode of the first instruction after the string. N.B. Cannot be used for BRK error messages -- the stack manipulation means a BRK in the inline data would corrupt the stack rather than invoke the error handler.

Advances Y past space characters in (fs_options),Y. Returns with the first non-space character in A. Sets carry if the character is >= 'A' (alphabetic).

Reads ASCII digits and accumulates in &B2 (fs_load_addr_2). Multiplication by 10 uses the identity: n*10 = n*8 + n*2, computed as ASL &B2 (x2), then A = &B2*4 via two ASLs, then ADC &B2 gives x10. Terminates on "." (pathname separator), control chars, or space. The delimiter handling was revised to support dot-separated path components (e.g. "1.$.PROG", on_entry={"y": "offset into (fs_options) buffer"}, on_exit={"a": "parsed value (accumulated in &B2)", "x": "initial A value (saved by TAX)", "y": "offset past last digit parsed"}) >= &40 (any letter), but the revision allows numbers followed by dots.

Transfers A to Y via TAY, then falls through to handle_to_mask_clc to clear carry and convert.

Clears carry to ensure handle_to_mask converts unconditionally. Falls through to handle_to_mask.

Converts fileserver handles to single-bit masks segregated inside the BBC. NFS handles occupy the &20-&27 range (base HAND=&20), which cannot collide with local filing system or cassette handles -- the MOS routes OSFIND/OSBGET/OSBPUT to the correct filing system based on the handle value alone. The power-of-two encoding allows the EOF hint byte to track up to 8 files simultaneously with one bit per file, and enables fast set operations (ORA to add, EOR to toggle, AND to test) without loops. Handle 0 passes through unchanged (means "no file", on_entry={"y": "handle number", "c": "0: convert, 1 with Y=0: skip, 1 with Y!=0: convert"}, on_exit={"a": "preserved", "x": "preserved", "y": "bitmask (single bit set) or &FF if handle invalid"}) has a built-in validity check: if the handle is out of range, the repeated ASL shifts all bits out, leaving A=0, which is converted to Y=&FF as a sentinel -- bad handles fail gracefully rather than indexing into garbage. Callers needing to move the handle from A use handle_to_mask_a; callers needing carry cleared use handle_to_mask_clc.

Inverse of Y2FS. Converts from the power-of-two FS format back to a sequential handle number by counting right shifts until A=0. Adds &1E to convert the 1-based bit position to a handle number (handles start at &1F+1 = &20). Used when receiving handle values from the fileserver in reply packets.

Prints A as a decimal number using repeated subtraction for each digit position (100, 10, 1). Leading zeros are printed (no suppression). Used to display station numbers.

Divides Y by A using repeated subtraction. Prints the quotient as an ASCII digit ('0'-'9'). Returns with the remainder in Y. X starts at &2F ('0'-1) and increments once per subtraction, giving the ASCII digit directly.