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