Appendix C

Examples of Current Processor-Specific BIOS Calling Sequences

C.1 8080/Z-80

Entry Points:: All BIOS entry points are given as offsets from the beginning of the BIOS code space. These locations should contain a JMP instruction to the appropriate address in BIOS.
Parameters:: When parameters are not being passed in a specified register, they are pushed on the stack. Offsets from top-of-stack are given, recognizing that the stack grows down.
Completion Code:: Return in register C.
Calling Sequence:: RSP will use the CALL instruction to call BIOS. Thus the return address is at (SP),(SP)+1. All registers are available for use by BIOS. BIOS should clean off the stack before returning to RSP.

Entry Point	Offset (hex)	Parameters
CONSOLEREAD	00	return data byte in Reg C
CONSOLEWRITE	03	write data byte in Reg C
CONSOLEINIT	06	UIR pointer at (SP)+2,(SP)+3
PRINTERREAD	09	return data byte in Reg C
PRINTERWRITE	0C	write data byte in Reg C
PRINTERINIT	0F	UIR pointer at (SP)+2,(SP)+3
DISKREAD	12	block no. at (SP)+2,(SP)+3 byte count at (SP)+4,(SP)+5 data area addr. at (SP)+6,(SP)+7 drive no. at (SP)+8 CONTROL byte at (SP)+9
DISKWRITE	15	block no. at (SP)+2,(SP)+3 byte count at (SP)+4,(SP)+5 data area addr. at (SP)+6,(SP)+7 drive no. at (SP)+8 CONTROL byte at (SP)+9
DISKINIT	18	drive no. in Reg C UIR pointer at (SP)+2,(SP)+3
REMOTEREAD	1B	return data byte in Reg C
REMOTEWRITE	1E	write data byte in Reg C
REMOTEINIT	21	UIR pointer at (SP)+2,(SP)+3

Entry Points:: All BIOS entry points are given as offsets from the beginning of the BIOS code space. These locations should contain a JMP instruction to the appropriate address in BIOS.
Parameters:: When parameters are not being passed in a specified register, they are pushed on the stack. Offsets from the address pointed to by S (described as (S)) are given, recognizing that the stack grows down and that S normally points to the first available address below valid data.
Completion Code:: Return in register X.
Calling Sequence:: RSP will use the JSR instruction to call BIOS. Thus the return address is at (S)+1,(S)+2. All registers are available for use. The stack should be cleaned off by BIDS before returning to RSP.

Entry Point	Offset (hex)	Parameters
CONSOLEREAD	00	return data byte in Reg A
CONSOLEWRITE	03	write data byte in Reg A
CONSOLEINIT	06	UIR pointer at (S)+3,(S)+4
PRINTERREAD	09	return data byte in Reg A
PRINTERWRITE	0C	write data byte in Reg A
PRINTERINIT	0F	UIR pointer at (S)+3,(S)+4
DISKREAD	12	block no. at (S)+3,(S)+4 byte count at (S)+5,(S)+6 data area addr. at (S)+7,(S)+8 drive no. at (S)+9,(S)+A CONTROL word at (S)+B,(S)+C
DISKWRITE	15	block no. at (S)+3,(S)+4 byte count at (S)+5,(S)+6 data area addr. at (S)+7,(S)+8 drive no. at (S)+9,(S)+A CONTROL word at (S)+B,(S)+C
DISKINIT	18	drive no. in Reg A UIR pointer at (S)+3,(S)+4
REMOTEREAD	1B	return data byte in Reg A.
REMOTEWRITE	1E	write data byte in Reg A.
REMOTEINIT	21	UIR pointer at (S)+3,(S)+4

Entry Points:: All BIOS entry points are given as offsets from the beginning of the BIOS code space. These locations should contain a JMP (extended) instruction to the appropriate address in BIOS.
Parameters:: When parameters are not being passed in a specified register, they are pushed on the stack. Offsets from the address pointed to by SP (described as (SP)) are given, recognizing that the stack grows down and that SP normally points to the first available address below valid data.
Completion Code:: Return in register B.
Calling Sequence:: RSP will use the JSR instruction to call BIOS. Thus the return address will be at (SP)+1,(SP)+2. All registers are available for use. The stack should be cleaned off by BIOS before returning to RSP.

Entry Point	Offset (hex)	Parameters
CONSOLEREAD	00	return data byte in Reg A
CONSOLEWRITE	03	write data byte in Reg A
CONSOLEINIT	06	UIR pointer at (SP)+3,(SP)+4
PRINTERREAD	09	return data byte in Reg A
PRINTERWRITE	0C	write data byte in Reg A
PRINTERINIT	0F	UIR pointer at (SP)+3,(SP)+4
DISKREAD	12	block no. at (SP)+3,(SP)+4 byte count at (SP)+5,(SP)+6 data area addr. at (SP)+7,(SP)+9 drive no. at (SP)+9,(SP)+A CONTROL word at (SP)+B,(SP)+C
DISKWRITE	13	block no. at (SP)+3,(SP)+4 byte count at (SP)+5,(SP)+6 data area addr. at (SP)+7,(SP)+9 drive no. at (SP)+9,(SP)+A CONTROL word at (SP)+B,(SP)+C
DISKINIT	18	drive no. in Reg A UIR pointer at (SP)+3,(SP)+4
REMOTEREAD	1B	return data byte in Reg A
REMOTEWRITE	1E	write data byte in Reg A
REMOTEINIT	21	UIR pointer at (SP)+3,(SP)+4

This page last regenerated Sun Jul 25 04:12:13 2010.