git.sur5r.net Git - cc65/blob - libsrc/nes/ppubuf.s

   1 ;
   2 ; Written by Groepaz/Hitmen <groepaz@gmx.net>
   3 ; Cleanup by Ullrich von Bassewitz <uz@cc65.org>
   4 ;
   5
   6
   7         .export         ppubuf_waitempty
   8         .export         ppubuf_wait
   9         .export         ppubuf_put
  10         .export         ppubuf_flush
  11         .include        "nes.inc"
  12
  13 .code
  14
  15 ; ------------------------------------------------------------------------
  16 ; ppubuf_waitempty
  17 ; Wait until buffer is empty
  18
  19 .proc   ppubuf_waitempty
  20
  21
  22 @wait:  lda     ringcount
  23         bne     @wait
  24         rts
  25
  26 .endproc
  27
  28
  29 ; ------------------------------------------------------------------------
  30 ; ppubuf_wait
  31 ; Wait until buffer is full
  32
  33 .proc   ppubuf_wait
  34
  35         lda     #$ff            ; (($0100/3)*1)
  36 @wait:  cmp     ringcount
  37         beq     @wait
  38         rts
  39
  40 .endproc
  41
  42 ; ------------------------------------------------------------------------
  43 ; Put a PPU-Memory write to buffer
  44 ; called from main program (not necessary when in vblank irq)
  45
  46 .proc   ppubuf_put
  47
  48         sta     ppuval
  49         sty     ppuhi
  50         stx     ppulo
  51
  52         jsr     ppubuf_wait             ; wait if buffer is full
  53
  54         ldy     ringwrite
  55         lda     ppuhi
  56         sta     ringbuff,y
  57         lda     ppulo
  58         sta     ringbuff+$0100,y
  59         lda     ppuval
  60         sta     ringbuff+$0200,y
  61
  62         iny
  63         sty     ringwrite
  64         inc     ringcount
  65         rts
  66
  67 .endproc
  68
  69 ; ------------------------------------------------------------------------
  70 ; Flush PPU-Memory write buffer
  71 ; called from vblank interupt
  72
  73 .proc   ppubuf_flush
  74
  75         ldy     ringcount
  76         bne     @doloop
  77         rts
  78
  79 @doloop:
  80         ldx     ringread
  81         lda     #$0e
  82         sta     temp
  83
  84 @loop:
  85 .repeat 5
  86         lda     ringbuff,x
  87         sta     $2006
  88         lda     ringbuff+$0100,x
  89         sta     $2006
  90         lda     ringbuff+$0200,x
  91         sta     $2007
  92         inx
  93
  94         dey
  95         beq     @end
  96 .endrepeat
  97
  98         dec     temp
  99         bne     @loop
 100
 101 @end:   stx     ringread
 102         sty     ringcount
 103
 104         rts
 105
 106 .endproc
 107
 108 ; ------------------------------------------------------------------------
 109 ; Data
 110
 111 .bss
 112
 113 temp:   .res    1
 114
 115