6 ; If open_apple key is pressed then the high-bit of the key is set.
10 .import cursor, putchardirect
21 lda #$7F | $80 ; Checkerboard, screen code
23 lda #' ' | $40 ; Blank, flashing
25 jsr putchardirect ; Returns old character in X
27 ; Wait for keyboard strobe.
29 bpl :- ; If < 128, no key pressed
35 ; Restore old character.
41 ; At this time, the high bit of the key pressed is set.
42 : bit KBDSTRB ; Clear keyboard strobe
44 bit BUTN0 ; Check if OpenApple is down
47 and #$7F ; If not down, then clear high bit