mirror of
https://github.com/cc65/cc65.git
synced 2024-12-25 02:29:52 +00:00
30 lines
885 B
PHP
30 lines
885 B
PHP
;
|
|
; Callback routine called from the IRQ handler after the ROM IRQ handler
|
|
; had been run.
|
|
;
|
|
; Christian Groessler, 24.04.2014
|
|
;
|
|
; Check if there was button/joystick activity before and/or after the ROM handler.
|
|
; If there was activity, discard the key presses since they are most
|
|
; probably "phantom" key presses.
|
|
|
|
callback:
|
|
ldx old_key_count
|
|
cpx KEY_COUNT
|
|
beq @nokey
|
|
|
|
lda OLD_BUTTONS ; keypress before?
|
|
bne @discard_key ; yes, discard key
|
|
|
|
lda #$7F
|
|
sta CIA1_PRA
|
|
lda CIA1_PRB ; Read joystick #0
|
|
and #$1F
|
|
eor #$1F ; keypress after
|
|
beq @nokey ; no, probably a real key press
|
|
|
|
@discard_key:
|
|
stx KEY_COUNT ; set old keyboard buffer fill level
|
|
|
|
@nokey: rts
|