MC68HC908GR16 Datasheet, PDF (111/310 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Keyboard Interrupt Module (KBI)
Functional Description
INTERNAL BUS
KBD0
VECTOR FETCH
DECODER
ACKK
RESET
TO PULLUP ENABLE
.
.
KB0IE
.
KBD7
V_DD
CLR
D
Q
CK
KEYF
SYNCHRONIZER
IMASKK
KEYBOARD
INTERRUPT
REQUEST
TO PULLUP ENABLE
KB7IE
MODEK
Figure 9-2. Keyboard Module Block Diagram
Addr.
$001A
$001B
Register Name
Bit 7
6
5
4
3
Keyboard Status Read:
and Control Register _Write:
(INTKBSCR)
See page 114. ^Reset:
Keyboard Interrupt Enable Read:
Register _Write:
(INTKBIER)
See page 115. ^Reset:
0
0
KBIE7
0
0
0
0
0
KBIE6 KBIE5
0
0
= Unimplemented
0
0
KBIE4
0
KEYF
0
KBIE3
0
Figure 9-3. I/O Register Summary
2
0
ACKK
0
1
Bit 0
IMASKK MODEK
0
0
KBIE2 KBIE1 KBIE0
0
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
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
MC68HC908GR16 — Rev. 1.0
MOTOROLA
Keyboard Interrupt Module (KBI)
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Data Sheet
111