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cc65/libsrc/atari/findfreeiocb.inc
2013-06-25 01:29:56 +02:00

24 lines
450 B
PHP

; find a free iocb
; no entry parameters
; return ZF = 0/1 for not found/found
; index in X if found
; all registers destroyed
.proc findfreeiocb
ldx #0
ldy #$FF
loop: tya
cmp ICHID,x
beq found
txa
clc
adc #$10
tax
cmp #$80
bcc loop
inx ; return ZF cleared
found: rts
.endproc ; findfreeiocb