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        "ONCE"
  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         jmp     SETVBV
  27
  28 ; ------------------------------------------------------------------------
  29
  30 .code
  31
  32 doneirq:
  33         lda     #7
  34         ldy     IRQInd+1
  35         ldx     IRQInd+2
  36         jmp     SETVBV
  37
  38 ; ------------------------------------------------------------------------
  39
  40 .segment        "LOWCODE"
  41
  42 IRQStub:
  43         cld                             ; Just to be sure
  44 .ifdef __ATARIXL__
  45 .ifdef CHARGEN_RELOC
  46         lda     CHBAS
  47         pha
  48 .endif
  49         lda     PORTB
  50         pha
  51         and     #$FE
  52         sta     PORTB                   ; disable ROM
  53         set_chbase >__CHARGEN_START__
  54 .endif
  55         jsr     callirq                 ; Call the functions
  56 .ifdef __ATARIXL__
  57         pla
  58         sta     PORTB                   ; restore old ROM setting
  59 .ifdef CHARGEN_RELOC
  60         pla
  61         sta     CHBAS
  62         sta     CHBASE
  63 .endif
  64 .endif
  65         jmp     IRQInd                  ; Jump to the saved IRQ vector
  66
  67 ; ------------------------------------------------------------------------
  68
  69 .data
  70
  71 IRQInd: jmp     $0000