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     VVBLKI
  20         ldx     VVBLKI+1
  21         sta     IRQInd+1
  22         stx     IRQInd+2
  23         lda     #6
  24         ldy     #<IRQStub
  25         ldx     #>IRQStub
  26         jsr     SETVBV
  27         rts
  28
  29 ; ------------------------------------------------------------------------
  30
  31 .code
  32
  33 doneirq:
  34         lda     #6
  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         pha
  48 .ifdef CHARGEN_RELOC
  49         lda     CHBAS
  50         pha
  51 .endif
  52         lda     PORTB
  53         pha
  54         and     #$FE
  55         sta     PORTB                   ; disable ROM
  56         set_chbase >__CHARGEN_START__
  57 .endif
  58         jsr     callirq                 ; Call the functions
  59 .ifdef __ATARIXL__
  60         pla
  61         sta     PORTB                   ; restore old ROM setting
  62 .ifdef CHARGEN_RELOC
  63         pla
  64         sta     CHBAS
  65         sta     CHBASE
  66 .endif
  67         pla
  68 .endif
  69         jmp     IRQInd                  ; Jump to the saved IRQ vector
  70
  71 ; ------------------------------------------------------------------------
  72
  73 .data
  74
  75 IRQInd: jmp     $0000