MC68HC908QY4A_10 Datasheet, PDF (85/200 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

INTERNAL BUS
Functional Description
KBI0
KBIP0
VECTOR FETCH
DECODER
ACKK
RESET
1
0S
KBIE0
TO PULLUP/
PULLDOWN ENABLE
V_DD
CLR
D
Q
CK
KEYF
SYNCHRONIZER
1
KBIx
0S
KBIPx
AWUIREQ
(SEE Figure 4-1)
KBIEx
TO PULLUP/
PULLDOWN ENABLE
KBI LATCH
MODEK
IMASKK
Figure 9-2. Keyboard Interrupt Block Diagram
KEYBOARD
INTERRUPT
REQUEST
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.
MC68HC908QYA/QTA Family Data Sheet, Rev. 3
Freescale Semiconductor
85