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cc65/libsrc/apple2/cgetc.s
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ArmAsm

;;
;; Kevin Ruland
;;
;; char cgetc (void);
;;
;; If open_apple key is pressed then the high-bit of the
;; key is set.
.export _cgetc
.include "apple2.inc"
_cgetc:
lda KEY_STROBE
bpl _cgetc ; if < 128, no key pressed
;; At this time, the high bit of the key pressed
;; is set
sta CLEAR_KEY_STROBE; clear keyboard strobe
bit OPEN_APPLE ; check if OpenApple is down
bmi pressed
and #$7F ; If not down, then clear high bit
pressed:
ldx #0
rts