Datasheet

Functional Description
MC68HC908QYA/QTA Family Data Sheet, Rev. 3
Freescale Semiconductor 85
Figure 9-2. Keyboard Interrupt Block Diagram
The KBI vector fetch or software clear and the return of all enabled keyboard interrupt pins to a deasserted
level may occur in any order.
Reset clears the keyboard interrupt request and the MODEK bit, clearing the interrupt request even if a
keyboard interrupt input stays asserted.
9.3.1.2 MODEK = 0
If the MODEK bit is clear, the keyboard interrupt inputs are edge sensitive. The KBIPx bit will determine
whether an edge sensitive pin detects rising or falling edges. A KBI vector fetch or software clear
immediately clears the KBI latch.
The keyboard flag bit (KEYF) in KBSCR can be read to check for pending interrupts. The KEYF bit is not
affected by IMASKK, which makes it useful in applications where polling is preferred.
NOTE
Setting a keyboard interrupt enable bit (KBIEx) forces the corresponding
keyboard interrupt pin to be an input, overriding the data direction register.
However, the data direction register bit must be a 0 for software to read the
pin.
KBI LATCH
KEYBOARD
INTERRUPT
REQUEST
ACKK
INTERNAL BUS
RESET
KBIE0
KBI0
0
1
S
KBIP0
KBIEx
KBIx
0
1
S
KBIPx
DQ
CK
CLR
V
DD
MODEK
IMASKK
SYNCHRONIZER
KEYF
TO PULLUP/
TO PULLUP/
PULLDOWN ENABLE
PULLDOWN ENABLE
VECTOR FETCH
DECODER
AWUIREQ
(SEE Figure 4-1)