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

   1 ;
   2 ; IRQ handling (PET version)
   3 ;
   4
   5         .export         initirq, doneirq
   6         .import         callirq
   7
   8         .include        "pet.inc"
   9
  10 ; ------------------------------------------------------------------------
  11
  12 .segment        "INIT"
  13
  14 initirq:
  15         lda     IRQVec
  16         ldx     IRQVec+1
  17         sta     IRQInd+1
  18         stx     IRQInd+2
  19         lda     #<IRQStub
  20         ldx     #>IRQStub
  21         sei
  22         sta     IRQVec
  23         stx     IRQVec+1
  24         cli
  25         rts
  26
  27 ; ------------------------------------------------------------------------
  28
  29 .code
  30
  31 doneirq:
  32         lda     IRQInd+1
  33         ldx     IRQInd+2
  34         sei
  35         sta     IRQVec
  36         stx     IRQVec+1
  37         cli
  38         rts
  39
  40 ; ------------------------------------------------------------------------
  41
  42 .segment        "LOWCODE"
  43
  44 IRQStub:
  45         cld                             ; Just to be sure
  46         jsr     callirq                 ; Call the functions
  47         jmp     IRQInd                  ; Jump to the saved IRQ vector
  48
  49 ; ------------------------------------------------------------------------
  50
  51 .data
  52
  53 IRQInd: jmp     $0000