MC68HC08AZ32A Datasheet, PDF (101/312 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Functional Description
INTERNAL BUS
KBD0
TO PULLUP
.
ENABLE
.
KB0IE
.
KBD4
TO PULLUP
ENABLE
KB4IE
V_DD
CLR
D
Q
CK
ACKK
RESET
VECTOR FETCH
DECODER
KEYF
SYNCHRONIZER
MODEK
KEYBOARD
INTERRUPT FF
IMASKK
KEYBOARD
INTERRUPT
REQUEST
Figure 8-2. Keyboard Module Block Diagram
Addr. Register Name
$001B
Keyboard Status and Control
Register (KBSCR)
Read:
Write:
See page 103. _Reset:
$0021
Keyboard Interrupt Enable ^Read:
Register (KBIER) Write:
See page 104. _Reset:
Bit 7
0
0
0
0
6
5
0
0
0
0
0
0
0
0
= Unimplemented
4
0
0
KBIE4
0
3
KEYF
0
KBIE3
0
2
0
ACKK
0
KBIE2
0
1
Bit 0
IMASKK MODEK
0
0
KBIE1 KBIE0
0
0
Figure 8-3. I/O Register Summary
If the MODEK bit is set, the keyboard interrupt pins are both falling edge- and low- level sensitive, and
both of the following actions must occur to clear a keyboard interrupt request:
• Vector fetch or software clear — A vector fetch generates an interrupt acknowledge signal to clear
the interrupt request. Software may generate the interrupt acknowledge signal by writing a 1 to the
ACKK bit in the keyboard status and control register (KBSCR). The ACKK bit is useful in
applications that poll the keyboard interrupt pins and require software to clear the keyboard
interrupt request. Writing to the ACKK bit prior to leaving an interrupt service routine also can
prevent spurious interrupts due to noise. Setting ACKK does not affect subsequent transitions on
the keyboard interrupt pins. A falling edge that occurs after writing to the ACKK bit latches another
interrupt request. If the keyboard interrupt mask bit, IMASKK, is clear, the CPU loads the program
counter with the KBI vector address.
• Return of all enabled keyboard interrupt pins to a high level. As long as any enabled keyboard
interrupt pin is low, the keyboard interrupt remains set.
The vector fetch or software clear and the return of all enabled keyboard interrupt pins to a high level may
occur in any order.
MC68HC08AZ32A Data Sheet, Rev. 2
Freescale Semiconductor
101