c64 rasterbars wip

rasterbars.asm

  processor 6502

  MACRO DELAY ;; {1} - loop iterations
    ldx {1}
.loop:
    dex
    bne .loop
  ENDM

  MACRO RASTER ;; {1} - background color to set
    lda {1}
    sta $d020
    sta $d021
  ENDM

  ;; VICE autostart logic
  org $0801
  .byte $0b, $08, $01, $00, $9e, $32, $30, $36
  .byte $31, $00, $00, $00

  ;; Interrupt logic
setup_interrupts:
  sei                  ; turn off interrupts
  lda #$7f
  sta $dc0d
  sta $dd0d
  lda #$01
  sta $d01a

  lda #<irq            ; set interrupt handler
  ldx #>irq
  sta $0314
  stx $0315

  ldy #$00             ; enable raster interrupts
  sty $d012

  lda $dc0d            ; acknowledge interrupts
  lda $dd0d
  asl $d019
  cli

  ;; Main loop
main_loop:
  jmp main_loop

  ;; Raster interrupt
irq:
  DELAY #$05
  RASTER #$06

  DELAY #$0a
  RASTER #$13

  DELAY #$0a
  RASTER #$0e

  DELAY #$0c
  RASTER #$03

  DELAY #$15
  RASTER #$01

  DELAY #$17
  RASTER #$03

  DELAY #$17
  RASTER #$0e

  DELAY #$17
  RASTER #$13

  DELAY #$17
  RASTER #$06

  DELAY #$0a
  RASTER #$00

  asl $d019            ; return from interrupt
  jmp $ea81