mirror of
https://github.com/RevCurtisP/C02.git
synced 2024-11-22 01:31:33 +00:00
83 lines
2.4 KiB
Plaintext
83 lines
2.4 KiB
Plaintext
|
; C02 Interrupt Vector Assembly Language Routines for VIC-20
|
||
|
|
|
||
|
|
;getirq() - Return IRQ Interrupt Handler Address
|
||
|
|
;Returns: A = $00 - Software Definable Address
|
||
|
|
; Y = Address MSB
|
||
|
|
; X = Address LSB
|
||
|
|
GETIRQ: LDA #$00 ;Return software definable
|
||
|
|
LDX $0314 ;and Address in CINV
|
||
|
|
LDY $0315
|
||
|
|
RTS
|
||
|
|
|
||
|
|
;getbrk() - Return BRK Interrupt Handler Address
|
||
|
|
;Returns: A = $00 - Software Definable Address
|
||
|
|
; Y = Address MSB
|
||
|
|
; X = Address LSB
|
||
|
|
GETBRK: LDA #$00 ;Return software definable
|
||
|
|
LDX $0316 ;and Address in CBINV
|
||
|
|
LDY $0317
|
||
|
|
RTS
|
||
|
|
|
||
|
|
;getnmi() - Return NMI Interrupt Handler Address
|
||
|
|
;Returns: A = $00 - Software Definable Address
|
||
|
|
; Y = Address MSB
|
||
|
|
; X = Address LSB
|
||
|
|
GETNMI: LDA #$00 ;Return software definable
|
||
|
|
LDX $0318 ;and Address in CBINV
|
||
|
|
LDY $0319
|
||
|
|
RTS
|
||
|
|
|
||
|
|
;getrst() - Return RESET Interrupt Handler Address
|
||
|
|
;Returns: A = $7F - Firmware Defined Address
|
||
|
|
; Y = Address MSB
|
||
|
|
; X = Address LSB
|
||
|
|
GETRST: LDX $FFFC ;Load 6502 Interrupt Vector
|
||
|
|
LDY $FFFD ;and Fall into SETRST
|
||
|
|
|
||
|
|
;setrst() - Set RESET Interrupt Handler Address
|
||
|
|
;Args: Y = Address MSB
|
||
|
|
; X = Address LSB
|
||
|
|
;Returns: A = $7F - Failure - Can't be Changed
|
||
|
|
SETRST: LDA #$7F ;Return "Hard Coded"
|
||
|
|
RTS
|
||
|
|
|
||
|
|
;setirq() - Set IRQ Interrupt Handler Address
|
||
|
|
;Args: Y = Address MSB
|
||
|
|
; X = Address LSB
|
||
|
|
;Returns: A = $00 - Successfully Set
|
||
|
|
SETIRQ: SEI ;Disable Interrupts
|
||
|
|
STX $0314 ;Store Address in CINV
|
||
|
|
STY $0315
|
||
|
|
CLI ;Enable Interrupts
|
||
|
|
LDA #$00 ;Return "Modified"
|
||
|
|
RTS
|
||
|
|
|
||
|
|
;setrst() - Set BRK Interrupt Handler Address
|
||
|
|
;Args: Y = Address MSB
|
||
|
|
; X = Address LSB
|
||
|
|
;Returns: A = $00 - Successfully Set
|
||
|
|
SETBRK: SEI ;Disable Interrupts
|
||
|
|
STX $0316 ;Store Address in CBINV
|
||
|
|
STY $0317
|
||
|
|
CLI ;Enable Interrupts
|
||
|
|
LDA #$00 Return "Modified"
|
||
|
|
RTS
|
||
|
|
|
||
|
|
;setnmi() - Set NMI Interrupt Handler Address
|
||
|
|
;Args: Y = Address MSB
|
||
|
|
; X = Address LSB
|
||
|
|
;Returns: A = $00 - Successfully Set
|
||
|
|
SETNMI: STX $0318 ;Store Address in NMINV
|
||
|
|
STY $0319
|
||
|
|
LDA #$00 ;Return "Modified"
|
||
|
|
RTS
|
||
|
|
|
||
|
|
;xitirq - Exit from IRQ Interrupt
|
||
|
|
;Exit IRQ if not Executing System IRQ Routine
|
||
|
|
XITIRQ: PLA ;Restore Y Register
|
||
|
|
TAY
|
||
|
|
PLA ;Restore Y Register
|
||
|
|
TAX
|
||
|
|
PLA ;Restore Accumulator
|
||
|
|
RTI ;Return from Interrupt
|