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28 lines
600 B
NASM
28 lines
600 B
NASM
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; kbd
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;
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; Control TI-84+'s keyboard.
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;
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; *** Constants ***
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.equ KBD_PORT 0x01
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; *** Code ***
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; Sending 0xff to the port resets the keyboard, and then we have to send groups
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; we want to "listen" to, with a 0 in the group bit. Thus, to know if *any* key
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; is pressed, we send 0xff to reset the keypad, then 0x00 to select all groups,
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; if the result isn't 0xff, at least one key is pressed.
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waitForKey:
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push af
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ld a, 0xff
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out (KBD_PORT), a
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ld a, 0x00
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out (KBD_PORT), a
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.loop:
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in a, (KBD_PORT)
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inc a ; if a was 0xff, will become 0 (z test)
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jr z, .loop ; zero? nothing pressed
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pop af
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ret
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