git.sur5r.net Git - cc65/blob - libsrc/atari/findfreeiocb.inc

   1 ; find a free iocb
   2 ; no entry parameters
   3 ; return ZF = 0/1 for not found/found
   4 ;        index in X if found
   5 ; all registers destroyed
   6
   7 .proc   findfreeiocb
   8
   9         ldx     #0
  10         ldy     #$FF
  11 loop:   tya
  12         cmp     ICHID,x
  13         beq     found
  14         txa
  15         clc
  16         adc     #$10
  17         tax
  18         cmp     #$80
  19         bcc     loop
  20         inx                     ; return ZF cleared
  21 found:  rts
  22
  23 .endproc        ; findfreeiocb