Key delay flag or key debounce counter; used to see if any key has been pressed. If a zero is returned, then no key has been pressed. If three is returned, then any key. It is decremented every stage two VBLANK (1/60 or 1/30th second) until it reaches zero. If any key is pressed while KEYDEL is greater than zero, it is ignored as "bounce."

see also: Keyboard topics, CH, CH1