mirror of
https://github.com/RevCurtisP/C02.git
synced 2024-11-25 21:33:44 +00:00
107 lines
3.3 KiB
Plaintext
107 lines
3.3 KiB
Plaintext
;C02 Interrupt Vector Assembly Language Routines for Apple 2
|
||
|
||
;getbrk() - Return BRK Interrupt Address
|
||
;Returns: A = $00 - Software Definable Address
|
||
; Y = Address MSB
|
||
; X = Address LSB
|
||
GETBRK: LDA #$00 ;Return software definable
|
||
LDX $03F0 ;and Address in Soft Break Vector
|
||
LDY $03F1
|
||
RTS
|
||
|
||
;getrst() - Return RST Interrupt Address
|
||
;Returns: A = $00 - Autostart ROM (Vectored through RAM)
|
||
; $7F - Monitor ROM (Hard Coded)
|
||
; Y = Address MSB
|
||
; X = Address LSB
|
||
GETRST: JSR GETRSC ;Check ROM Version
|
||
BNE GETRSX ;If Autostart ROM
|
||
LDX $03F2 ; Return Address in Soft Reset Vector
|
||
LDY $03F3
|
||
RTS
|
||
GETRSX: LDX $FFFC ;Else
|
||
LDY $FFFD ; Return Address in 6502 RESET Vector
|
||
RTS
|
||
|
||
;Check 6502 RESET Vector
|
||
;Returns: A = $00 - Autostart ROM (Vectored through RAM)
|
||
; $7F - Monitor ROM (Hard Coded)
|
||
;Notes: $FFFC contains $FF59 on Apple ][ (Monitor ROM)
|
||
; $FA62 on all other machines (Autostart ROM)
|
||
GETRSC: LDA $FFFD ;Load MSB of Vector
|
||
CMP #$FF ;
|
||
BEQ GETRSF ;If Not Monitor ROM
|
||
LDA #$00 ; Return $00
|
||
RTS
|
||
GETRSF: LDA #$7F ;Else Return $FF
|
||
RTS
|
||
|
||
;getnmi() - Return NMI Interrupt Address
|
||
;Returns: A = $00 - Software Definable Address
|
||
; Y = Address MSB
|
||
; X = Address LSB
|
||
;Notes: $FFFA contains $03FB in all ROMs
|
||
GETNMI: LDA #$00 ;Return software definable
|
||
LDX $03FB ;and Address in NMI vector
|
||
LDY $03FC
|
||
RTS
|
||
|
||
;getirq() - Return IRQ Interrupt Address
|
||
;Returns: A = $00 - Software Definable Address
|
||
; Y = Address MSB
|
||
; X = Address LSB
|
||
;Notes: $FFFE contains $FA86 on Apple ][ (Monitor ROM)
|
||
; $FA40 on Apple ][+ and Pravets
|
||
; $C3FA on Apple //e, $FAC3 on TK3000//e
|
||
; $FF59 on Franklin 1000 and Laser 128
|
||
GETIRQ: LDA #$00 ;Return software definable
|
||
LDX $03FE ;and Address in CINV
|
||
LDY $03FF
|
||
RTS
|
||
|
||
;setbrk() - Set BRK Interrupt Address
|
||
;Args: Y = Address MSB
|
||
; X = Address LSB
|
||
;Returns: A = $00 - Successfully Set
|
||
SETBRK: SEI ;Disable Interrupts
|
||
STX $03F0 ;Store Address in Soft Rreak Vector
|
||
STY $03F1
|
||
CLI ;Enable Interrupts
|
||
LDA #$00 ;Return Success
|
||
RTS
|
||
|
||
;setrst() - Set RST Interrupt Address
|
||
;Args: Y = Address MSB
|
||
; X = Address LSB
|
||
;Returns: A = $00 If Autostart ROM (Success)
|
||
; $7F If Monitor ROM (Failure)
|
||
SETRST: JSR GETRSC ;Check ROM Version
|
||
BNE SETRSX ;If Autostart ROM
|
||
SEI ; Disable Interrupts
|
||
STX $03F2 ; Store Address in Soft Reset Vector
|
||
STY $03F3
|
||
CLI ; Enable Interrupts
|
||
SETRSX: RTS
|
||
|
||
;setnmi() - Set NMI Interrupt Address
|
||
;Args: Y = Address MSB
|
||
; X = Address LSB
|
||
;Returns: A = $00 - Successfully Set
|
||
SETNMI: SEI ;Disable Interrupts
|
||
STX $03FB ;Store Address in NMI vector
|
||
STY $03FC
|
||
CLI ;Enable Interrupts
|
||
LDA #$00 ;Return Success
|
||
RTS
|
||
|
||
;setirq() - Set Maskable Interrupt Address
|
||
;Args: Y = Address MSB
|
||
; X = Address LSB
|
||
;Returns: A = $00 - Successfully Set
|
||
SETIRQ: SEI ;Disable Interrupts
|
||
STX $03FE ;Store Address in ????
|
||
STY $03FF
|
||
CLI ;Enable Interrupts
|
||
LDA #$00
|
||
RTS
|