MC68HC908GZ8 Datasheet, PDF (140/344 Pages) Motorola, Inc – Microcontrollers

Keyboard Interrupt Module (KBI)
INTERNAL BUS
KBD0
VECTOR FETCH
DECODER
ACKK
RESET
TO PULLUP ENABLE
.
.
KB0IE
.
KBD7
V_DD
D ^CLR Q
CK
KEYF
SYNCHRONIZER
IMASKK
TO PULLUP ENABLE
KB7IE
MODEK
Figure 13-1. Keyboard Module Block Diagram
KEYBOARD
INTERRUPT
REQUEST
Addr.
$001A
$001B
Register Name
Keyboard Status Read:
and Control Register
(INTKBSCR)
Write:
See page 143. ^Reset:
Keyboard Interrupt Enable Read:
Register
(INTKBIER)
Write:
See page 144. ^Reset:
Bit 7
0
0
KBIE7
0
6
5
0
0
0
0
KBIE6 KBIE5
0
0
= Unimplemented
4
0
0
KBIE4
0
3
KEYF
0
KBIE3
0
Figure 13-2. I/O Register Summary
2
0
ACKK
0
KBIE2
0
1
Bit 0
IMASKK MODEK
0
0
KBIE1 KBIE0
0
0
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 logic 1 to the ACKK bit in the
keyboard status and control register (INTKBSCR). 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 can also prevent spurious interrupts due to
Data Sheet
140
Keyboard Interrupt Module (KBI)
MC68HC908GZ8
Freescale Semiconductor