cbios/fifo.180

   1
   2         public  bufinit
   3         public  ff_empty,ff_get,ff_full,ff_put
   4
   5         public  fifolst
   6
   7         extrn   msg.sm,hwl2phy
   8
   9         include config.inc
  10         include z180reg.inc
  11
  12
  13 ;--------------------------------------------------------------------
  14
  15         dseg
  16
  17 fifolst:
  18         rept 4
  19          dw     0
  20         endm
  21
  22 ;--------------------------------------------------------------------
  23
  24         dseg
  25
  26 bufinit:
  27         ld      (ix+o.in_idx),0         ;reset pointers (empty fifo)
  28         ld      (ix+o.out_idx),0
  29         ld      a,(ix+o.id)
  30         ld      hl,fifolst
  31         ld      e,a
  32         ld      d,0
  33         add     hl,de
  34         add     hl,de
  35         push    ix
  36         pop     de
  37         cp      4
  38         jr      nc,bfi_skip
  39
  40         ld      (hl),e
  41         inc     hl
  42         ld      (hl),d
  43
  44 bfi_skip:
  45         ex      de,hl
  46         call    hwl2phy                 ;get phys. address of fifo
  47         ld      c,a
  48         ld      a,(ix+o.id)             ;fifo id
  49         or      a                       ;test if fifo 0
  50         ret     z
  51
  52         cp      4
  53         ret     nc
  54
  55 ; TODO: move to better place
  56
  57         ld      b,a
  58         push    bc                      ;c: bank-addr, b: ignored
  59         push    hl                      ;address
  60         ld      c,0
  61         push    bc                      ;c: function, b:subf
  62         ld      b,5
  63         ld      h,c
  64         ld      l,c
  65         add     hl,sp
  66         call    msg.sm
  67         pop     hl
  68         pop     hl
  69         pop     hl
  70         ret
  71
  72 ;--------------------------------------------------------------
  73 ; Check if characters in fifo
  74 ; Fifo is empty, if output index and input index are the same
  75
  76 ff_empty:
  77         ld      a,(ix+o.in_idx)         ;
  78         sub     (ix+o.out_idx)          ;
  79         ret     z
  80         or      0ffh
  81         ret
  82
  83 ;--------------------------------------------------------------
  84
  85 ff_get:
  86         push    ix
  87         pop     hl
  88         ld      c,(ix+o.out_idx)        ;
  89         ld      b,0
  90         add     hl,bc
  91         ld      a,c
  92 bg.wait:
  93         cp      (ix+o.in_idx)           ;
  94         jr      z,bg.wait
  95         ld      b,(hl)
  96         ld      a,c                     ;
  97         inc     a
  98         and     (ix+o.mask)
  99         ld      (ix+o.out_idx),a
 100         ld      a,b
 101         ret
 102
 103 ;--------------------------------------------------------------
 104 ; Check if room in fifo
 105 ; buffer is full, if output index is one behind input index
 106
 107 ff_full:
 108         ld      a,(ix+o.in_idx)         ;
 109         inc     a
 110         and     (ix+o.mask)
 111         sub     (ix+o.out_idx)          ;
 112         ret     z
 113         or      0ffh
 114         ret
 115
 116
 117 ;--------------------------------------------------------------
 118 ; put character in c in buffer
 119 ; destroys hl, bc
 120 ; returns output char in a
 121
 122 ff_put:
 123         push    ix                      ;
 124         pop     hl                      ; get buffer start address
 125
 126         ld      a,c                     ;
 127         ld      c,(ix+o.in_idx)         ; add input index
 128         ld      b,0                     ;
 129         add     hl,bc                   ;
 130         ld      (hl),a                  ; one place is allways free
 131         ld      b,a                     ;
 132
 133         ld      a,c                     ; bump input index
 134         inc     a                       ;
 135         and     (ix+o.mask)             ;
 136 bp.wait:                                ; do
 137         cp      (ix+o.out_idx)          ;
 138         jr      z,bp.wait               ; while new input idx == ouput idx
 139         ld      (ix+o.in_idx),a         ;
 140         ld      a,b                     ;
 141         ret                             ;
 142
 143         end