The Amstrad extended BIOS is accessed using the USERF BIOS function. To call it, use:
CALL USERF DEFW valueThe value is a 16-bit address in memory bank 0 (user programs normally run in bank 1). The (documented) XBIOS jumpblock starts at 0080h and runs up to 00EEh.
My implementation of CP/M on the PCW16 supports calls from TE_ASK up to BANK2_RUN_ROUTINE.
Since the address of USERF may vary from computer to computer, the following subroutine should be used to access it in a machine-independent way:
USERF: PUSH HL PUSH DE LD HL,(1) LD DE,57h ADD HL,DE POP DE EX (SP),HL RETFrequently, these routines will require an address to be passed to them. Unless they are being called from within Bank 0, the address should be above 0C000h so that it is visible to the routine. The alternate register set is preserved during the call, but the values of the alternate registers will not be available to the called routine.
Initialise the floppy disc driver.
When called, this resets the floppy drives to their default parameters (for 3" or 3.5" drives, depending on computer), and turns the disc motor off. Corrupts AF,BC,DE,HL.
Set up the floppy disc driver.
Entered with: HL=address of parameter block, above 0C000h. Corrupts AF, BC, DE and HL. The parameter block is formed:
DB motor on timeout, 10ths of a second DB motor off timeout, 10ths of a second DB write current off time in 10 uS units DB head settle time, milliseconds. DB step rate, milliseconds. DB head unload delay in 32ms units. DB (2*head load delay in 4ms units)+non DMA mode.
[Recent PCW versions only] If HL=0, set up only one drive - the one whose number is given in C. DE holds the address of the parameter block.
Read a floppy disc sector.
Entered with: B=CP/M bank, C=disc unit(0 or 1), D=track(0 based), E=sector (0 based), HL=load address within bank, IX=address of drive XDPB.
Returns: Carry set if OK, reset if error. A=error number 0-9. BC, DE and HL are corrupted.
0: Drive not ready 1: Write protected 2: Seek fail 3: Data error 4: No data 5: Missing address mark 6: Bad format 7: Unknown error 8: Media changed 9: Unsuitable media
Write a floppy disc sector.
Entered with: B=CP/M bank, C=disc unit(0 or 1), D=track(0 based), E=sector (0 based), HL=address within bank of sector, IX=address of drive XDPB.
Returns: Carry set if OK, reset if error. A=error number 0-9. BC, DE and HL are corrupted.
Verify a floppy disc sector.
Entered with: B=CP/M bank, C=disc unit(0 or 1), D=track(0 based), E=sector (0 based), HL=address within bank of sector, IX=address of drive XDPB.
Returns: If error: Carry reset, A=error number 0-9. If no error, Carry set, Zero set if sector matched sector in memory. Otherwise Zero reset. BC, DE and HL are corrupted.
Format a floppy disc track.
Entered with: B=CP/M bank, C=disc unit(0 or 1), D=track(0 based), E=filler byte, HL=address within bank of format data, IX=address of drive XDPB.
Returns: If error: Carry reset, A=error number 0-9. If no error, Carry set. BC, DE and HL are corrupted.
The format data area is a list of sectors; each entry occupies four bytes. The entry for a sector is laid out as:
DB track number DB head number DB sector number DB physical sector shift. 0 => 128, 1 => 256, 2 => 512...
Log in a floppy disc.
Entered with: C=disc unit(0 or 1), IX=address of drive XDPB.
Returns: If OK, carry set, A=format type, BC corrupt, DE=size of double-bit allocation vector, HL=size of hash table, XDPB initialised. If error, A=error number, BC DE HL XDPB corrupt.
Format types are:
0: PCW Single Sided Single Density 1: CPC System format 2: CPC Data format 3: PCW Double Sided Double Density
Preload an XDPB with a standard format.
Entered with: A=format IX=address of destination XDPB.
Returns: If OK, carry set, A=format type, BC corrupt, DE=size of double-bit allocation vector, HL=size of hash table, XDPB initialised. If error, A=error number, BC DE HL XDPB corrupt.
Format types are:
0: PCW standard SS/SD, 173k 1: CPC System format, 169k 2: CPC Data format, 180k 3: PCW standard DS/DD, 706k
Get the drive status.
Entered with: C=disc unit(0 or 1); bit 2 of C contains head number.
Returns HL corrupt, A=uPD765a status register 3:
bit 7: ? bit 6: Write protected bit 5: Ready if bits 5 and 6 are zero the drive is not present. bit 4: Track 0 bit 3: ? bit 2: Head bit 1: Unit high bit (always zero, Units 2-3 are not implemented). bit 0: Unit low bit
Read a sector ID.
Entered with: C=disc unit(0 or 1); D=track(0 based); IX=address of XDPB.
Returns: If OK, Carry set, A=physical sector number. If error, Carry reset, A=error number. Always, BC and DE are corrupt and HL=address of FDC output buffer:
DB number-of-result-bytes DB result bytes
Initialise a DPB from a boot record.
Entered with: HL=address of boot record. IX=address of DPB.
Returns: If carry set, OK, A=disc type (as for DD LOGIN). If carry clear, A=error number. BC DE and HL are always corrupted.
Note: This function always fails on the CPC6128.
Initialise an XDPB from a boot record.
Entered with: HL=address of boot record. IX=address of XDPB.
Returns: If carry set, OK, A=disc type (as for DD LOGIN). If carry clear, A=error number. BC DE and HL are always corrupted.
Note: This function always fails on the CPC6128.
Turn the floppy drive motors on.
Preserves all registers and flags. Waits until the motors have spun up to speed before returning.
Start countdown for turning the motors off.
Preserves all registers and flags.
Switch the floppy drive motors off immediately.
Corrupts AF, BC, DE and HL.
Execute a uPD765A read command.
Entered with: HL=address of input buffer.
DB CP/M bank DW address of data buffer within bank DW number of data bytes DB number of uPD765a command bytes DB uPD765a command bytesReturns AF, BC, DE corrupt; HL=address of results buffer:
DB number of result bytes DB result bytesThe floppy drive motors must be running.
Execute a uPD765A write, scan or format command.
Entered with: HL=address of input buffer.
CP/M pages
DB CP/M bank
DW address of data buffer within bank
DW number of data bytes
DB number of uPD765a command bytes
DB uPD765a command bytes
Returns AF, BC, DE corrupt; HL=address of results buffer:
DB number of result bytes
DB result bytes
The floppy drive motors must be running.
Seek to a track.
Entered with: C=disc unit+4*head, D=cylinder number, IX=address of XDPB.
Initialise serial port.
Entered with: A=mode or command. If A is a mode, D=no. of stop bits, E=parity, H=number of receiver data bits, L=number of transmitter data bits.
Corrupts AF, BC, DE and HL.
Modes:
00h - No handshake 0FFh - Handshake 0FEh - Interrupt, no handshake (on Spectrum +3, behaves as 00h). 0FDh - Interrupt, handshake (on Spectrum +3, behaves as 0FFh).Commands:
80h - Drop DTR 7Fh - Raise DTR 7Eh - Drop RTS (no effect on Spectrum +3) 7Dh - Raise RTS (no effect on Spectrum +3)Number of stop bits:
D=0 1 stop bit D=1 1.5 stop bits (on Spectrum +3, behaves as D=2) D=2 2 stop bitsParity:
E=0 None E=1 Odd E=2 Even
Set SIO baud rate.
Entered with: H=receiver baudrate, L=transmitter baudrate.
Corrupts AF, BC, DE, HL.
Baud rates are numbered from 1-15; see here.
Get SIO parameters.
Returns registers containing parameters as set by CD SA INIT.
Get screen size and cursor position.
Returns:
B=top row of viewport in physical screen coordinates on CPC6128, BC is C=left column of viewport in physical screen coordinates always zero. D=height of viewport-1 E=width of viewport-1 H=cursor row, viewport coordinates L=cursor column, viewport coordinates
Implemented on the PCW16.
Reset the terminal emulator.
Corrupts AF, BC, DE and HL.
Resets viewport to full screen, character set to Language 0 (USA), no special effects, screen colours to default, cursor enabled etc. Can be called if the screen has been altered by other programs than the CRT driver.
Implemented on the PCW16.
Is the status line enabled?
Returns: A=0 if status line disabled, 0FFh if enabled. Zero false if status line visible, true if not visible.
On the +3, the status line can be enabled and invisible.
Implemented on the PCW16, though nothing is ever displayed on the status line.
Turn the status line on or off.
Entered with: A=0 for off or 0FFh for on. Corrupts F, BC, DE, HL.
The status line, if enabled, displays BIOS error messages and the status of the PCW's built-in printer. If it is disabled, BIOS error messages go to the main screen.
A similar status line is used in DOS Plus, where it lists the names of programs running in the background.
Implemented on the PCW16, though nothing is ever displayed on the status line.
Set screen palette.
Entered with: A=ink id; B=colour; C=flash value.
Corrupts AF, BC, DE and HL.
The ink number for B on the CPC, +3 and PCW16 is computed thus:
Bits 0-1: Blue Bits 2-3: Red Bits 4-5: Green Bits 6-7: IgnoredThe RGB values are:
00 Colour is off 01 Colour is on, low intensity [CPC]/ normal intensity [Spectrum and PCW16] 10 Colour is on, normal intensity 11 Colour is on, high intensityBUG: This function does not work under PCW or +3 CP/M, because the values in B and C are always reset to zero before they are examined.
Set screen border colour.
Entered with: B=colour, as above.
Corrupts AF, BC, DE and HL.
On the PCW, bit 7 of B is set for reversed video (dark text on light background) and bit 6 is set if the screen is to be blank.
Implemented on the PCW16.
Set colour flash speed.
Entered with: H=time spent in main colour, L=time spent in alternative colour, specified in 50ths of a second.
Corrupts AF and HL.
Has no effect on a Spectrum +3 or a PCW16.
Set a keyboard expansion string.
Entered with: B=string number, 80h-9Eh; C=length of string; HL=address of string.
Returns: If OK, Carry set. If string too long or B invalid, Carry clear. A, BC, DE, HL corrupted.
Implemented on the PCW16.
Set what character a keypress translates to.
Entered with: B=ASCII value, C=key number, D=bitmap of shift states.
Corrupts AF and HL.
On the PCW16, the key number is the Rosanne code corresponding to that keynumber and shift state (except for keypad keys).
Special ASCII values are:
If a bit is set in the shift states bitmap, it indicates that the table for that combination of shift keys should be modified. The bits mean:
0 - Unshifted keys 1 - SHIFT [PCW & PCW16], CAPS SHIFT [Spectrum +3] 2 - ALT [PCW], SYMBOL SHIFT [Spectrum +3], CTRL [PCW16] 3 - SHIFT+ALT [PCW], EXTEND [Spectrum +3], SHIFT+CTRL [PCW16] 4 - EXTRA [PCW], TASK [PCW16]
Get a character/key number.
Returns C=character, B=0.
If key pressed, returns C=key number, B=shift bitmap. If not, returns carry false, C corrupt, B=shift bitmap. Corrupts A.
The shift bitmap is:
Bit 0 not defined Bit 1 EXTRA Bit 2 Generated by a key repeat Bit 3 Caps lock Bit 4 Num lock Bit 5 SHIFT [PCW]; CAPS [Spectrum +3] Bit 6 Shift lock Bit 7 ALT [PCW]; SYMB [Spectrum +3]
If key pressed, returns C=keycode, B=Rosanne shift state. If not, returns BC corrupt. Always corrupts A.
Simulate a keypress..
Entered with: B=shift bitmap, C=key number.
On the +3 and PCW, the shift bitmap is:
Bit 0 not defined Bit 1 EXTRA [PCW]; EXTEND [+3] Bit 2 Generated by a key repeat Bit 3 Caps lock Bit 4 Num lock Bit 5 SHIFT [PCW]; CAPS [Spectrum +3] Bit 6 Shift lock Bit 7 ALT [PCW]; SYMB [Spectrum +3]On the CPC, this function has no effect. The main use of this function is to change the state of Caps/Num/Shift lock; use KM KT PUT to change the lock, and KM KT GET to swallow the simulated keypress. The PCW shift lock is implemented in hardware and so cannot be changed by this call.
On the +3, Shift lock operates on the CAPS SHIFT key.
On the PCW16, B and C are a Rosanne shift bitmap and keycode respectively. The Caps/Num/Shift locks are not implemented.
Set the keyboard reset speed..
Entered with: H=initial delay, L=subsequent delay.
Corrupts AF.
Both delays are given in fiftieths of a second. 0 means 256, ie keys hardly ever repeat. The initial delay takes place before a key repeats at all; the subsequent delay takes place between further repetitions.
Implemented on the PCW16.
Get version numbers. Supported on the PCW16..
Returns: A=machine type, B=BIOS major version number, C=BIOS minor version number, HL=machine specific version number.
Machine types are:
0 CPC6128 1 PCW8000/9000/10 series 3 Spectrum +3 65 PCW16 (65 = 'A', ie "Anne")The BIOS major version number is 2 for a PCW9512 or 9512+, 1 otherwise.
On a CPC6128, the machine specific version number is the ROM version.
On recent versions of PCW CP/M, H=0 and L is a bitmap of hardware detected:
On earlier PCW versions this word is zero.
On the PCW16, the machine specific version number is the address in bank 0 of a zero-terminated ASCII string containing the Rosanne version.
Get system information..
Returns: A=0FFh if second floppy drive fitted, otherwise 0; B=memory size/16k; C=0FFh if serial port present, otherwise 0; DE corrupt; HL=address of buffer table.
The buffer table holds addresses of disc buffers:
DB CP/M bank, 0FFh for end of table DW start DW length
Implemented on the PCW16, but HL returns 0.
On recent PCW versions, DE is not in fact corrupt, but holds flags for the two floppy drives (E = flags for A: D = flags for B:). The flags seem to be:
Run a routine with the screen memory visible.
Entered with: BC=address of routine. DE, HL, IX and IY are passed to it.
Returns BC corrupt; AF, DE, HL, IX, IY as returned by routine.
This routine does not exist in CPC6128 CP/M. Instead of using:
LD BC,routine CALL USERF DEFW 00E9hthe routine
CALL USERF DEFW routineshould be used. On the Spectrum +3, the above calls have an identical effect. On the PCW, however, the screen environment is unique and can only be accessed using this function.
The screen is located at:
The character sets are located at:
Find the address of an installable device driver. Supported on the PCW16.
Entered with: DE=address of name (8 characters).
Returns: Carry true if driver present, HL=address of driver in bank 0 (PCW16: bank 2). Else carry false, HL corrupt. Always corrupts A,BC,DE.
This routine is only present in +3 CP/M, PCW CP/M versions higher than about 1.7, and PCW16 CP/M. It should not be called otherwise!
Some FID names you can try are:
Run a routine with bank 2 visible.
Entered with: BC=address of routine. DE, HL, IX and IY are passed to it.
Returns BC corrupt; AF, DE, HL, IX, IY as returned by routine.
This works identically to SCR RUN ROUTINE, but calls code in bank 2.
The following calls are present in version 1.4 of the PCW XBIOS, and are included simply for completeness:
00ECh: Initialise the XBIOS 00EFh: Is character device B ready to input? 00F2h: Input character from device B 00F5h: Is device B ready to output? 00F8h: Output character C to device B 00FBh: Initialise device C, B=baudrate 00FEh: Display error message, ask whether to retry, ignore or cancel. 0101h: Ask user to insert the disc for A: or B:. 0104h: Output a system message. 0107h: Used by XMOVE and MOVE.
The following calls are present in version 1.15 of the PCW XBIOS, and are included for completeness and for comparison with the 1.4 calls above:
00EFh: ?
00F2h: Initialise the XBIOS.
00F5h: SVC_D_CHANGED - report that
the disc in drive B may have been changed.
00F8h: ?
00FBh: Display error message, ask whether to retry, ignore or cancel.
00FEh: Ask user to insert the disc for A: or B:.
0101h: Output a system message.
0104h: Used by XMOVE and MOVE.