git.sur5r.net Git - cc65/blob - libsrc/atari/irq.s

   1 ;
   2 ; IRQ handling (ATARI version)
   3 ;
   4
   5         .export         initirq, doneirq
   6         .import         callirq
   7
   8         .include        "atari.inc"
   9 .ifdef __ATARIXL__
  10         .import         __CHARGEN_START__
  11         .include        "romswitch.inc"
  12 .endif
  13
  14 ; ------------------------------------------------------------------------
  15
  16 .segment        "INIT"
  17
  18 initirq:
  19         lda     VVBLKD
  20         ldx     VVBLKD+1
  21         sta     IRQInd+1
  22         stx     IRQInd+2
  23         lda     #7
  24         ldy     #<IRQStub
  25         ldx     #>IRQStub
  26         jsr     SETVBV
  27         rts
  28
  29 ; ------------------------------------------------------------------------
  30
  31 .code
  32
  33 doneirq:
  34         lda     #7
  35         ldy     IRQInd+1
  36         ldx     IRQInd+2
  37         jsr     SETVBV
  38         rts
  39
  40 ; ------------------------------------------------------------------------
  41
  42 .segment        "LOWCODE"
  43
  44 IRQStub:
  45         cld                             ; Just to be sure
  46 .ifdef __ATARIXL__
  47 .ifdef CHARGEN_RELOC
  48         lda     CHBAS
  49         pha
  50 .endif
  51         lda     PORTB
  52         pha
  53         and     #$FE
  54         sta     PORTB                   ; disable ROM
  55         set_chbase >__CHARGEN_START__
  56 .endif
  57         jsr     callirq                 ; Call the functions
  58 .ifdef __ATARIXL__
  59         pla
  60         sta     PORTB                   ; restore old ROM setting
  61 .ifdef CHARGEN_RELOC
  62         pla
  63         sta     CHBAS
  64         sta     CHBASE
  65 .endif
  66 .endif
  67         jmp     IRQInd                  ; Jump to the saved IRQ vector
  68
  69 ; ------------------------------------------------------------------------
  70
  71 .data
  72
  73 IRQInd: jmp     $0000