timed_getch.s


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 .export _timed_getch, _set_jiffy_timer
 .import _cgetc

_set_jiffy_timer:
 sei
 sta 540
 stx 541
 cli
 rts

_timed_getch:
 jsr _set_jiffy_timer
wait4key:
 lda 540
 ora 541
 beq done
 ldx 764
 inx
 beq wait4key
 jmp _cgetc

done:
 lda #$ff ; return -1
 tax
 rts