SuperCPU Tutorial Listings - Part 7

Listing 7.1

; 65816 Native Mode IRQ-Programming
; written in 1997 by Malte Mundt
; for GO64!

 £ba $c000

 £la rasterpointer=$02


          sei
          clc             ; native mode
          xce

          lda #$35        ; disable rom
          sta $01
          lda #$01        ; enable
          sta $d01a       ; raster-irq
          lda #$1b        
          sta $d011
          lda #$61        ; at position $61
          sta $d012
          lda #$7f        ; disable cia-irq
          sta $dc0d       ; 
          lda $dc0d       ; clear poss. old cia irq
          lda #$00
          sta $d020
          sta $d021

          lda $d019       ; vic-
          sta $d019       ; irq clr

          lda #irq       ; native
          sta $ffef       ; vector

          cli

loop:
          sep #$30        ; 8 bit
          inc $d800       ; color-ram +1
          rep #$30        ; 16 bit      
          inc $0400       ; $0400/01 +1
          jmp loop                      

irq:
          pha             ; save accu
          phx             ; save x
          php             ; save status

          sep #$10        ; index 8 bit
          rep #$20        ; akku 16 bit
 £al
 £rs
          ldx rasterpointer
          lda coltab,x    ; get 16 bit
          sta $d020       ; to $d020/21

          sep #$20        ; accu 8 bit
 £as
          inc $d012       ; new irq
          inx             ; inc x by 2
          inx
          cpx #12
          bne skip
          lda #$61        ; next
          sta $d012       ; frame
          ldx #0

skip:
          stx rasterpointer

          lda $d019
          sta $d019

          plp             ; reset status
          pla             ; reset accu
          plx             ; reset x
          rti

coltab:
 £by $06,$02
 £by $0e,$0a
 £by $01,$07
 £by $0e,$0a
 £by $06,$02
 £by $00,$00

Assembler Code © by Malte Mundt

Partial translation and cosmetical changes by Count Zero/SCS*TRC

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