I said:
"the 'usual' method is to look for a key in sleep mode an to look for 'no key' in awake mode. on the 'no key' interrupt you can set the look for keey again to catch keys during awake."

I do not undestand why KBIF may not be used when uC is awake

I did not discuss using the KBI in "awake" (if I gave that impression, sorry). What you need to do is to set the (mis)match to something that you want to generate the interrupt. This can be tricky, but here is something to try: On KBI set the interrupt to match "no key" this wil generate an interrupt when the key is released. On that interrupt set the KBI for mismatch "no key" which then will give an int on the next keypress.

HOWEVER, that would be 'silly' the KBI is singularily unsuited for anything but "wake up" because it interfer with debouncing which is so much easier done with a keyscan in a timer interrupt.

Erik