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C02/include/apple2/vectors.a02
2019-03-22 20:14:58 -04:00

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;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