MC68HC908KX8 Datasheet, PDF (173/310 Pages) Motorola, Inc – Microcontrollers

Keyboard Interrupt Module (KBI)
Functional Description
Addr. Register Name
Bit 7
Read: 0
Keyboard Status and
$001A Control Register (KBSCR) Write:
See page 177.
Reset: 0
Read: 0
Keyboard Interrupt Enable
$001B
Register (KBIER) Write:
See page 178.
Reset: 0
6
5
0
0
0
0
0
0
0
0
= Unimplemented
4
3
2
1
Bit 0
0
KEYF
0
IMASKK MODEK
ACKK
0
0
0
0
0
KBIE4 KBIE3 KBIE2 KBIE1 KBIE0
0
0
0
0
0
Figure 13-2. I/O Register Summary
13.4 Functional Description
Writing to the KBIE4–KBIE0 bits in the keyboard interrupt enable register
independently enables or disables each port A pin as a keyboard
interrupt pin. Enabling a keyboard interrupt pin also enables its internal
pullup device. A logic 0 applied to an enabled keyboard interrupt pin
latches a keyboard interrupt request.
A keyboard interrupt is latched when one or more keyboard pins goes
low after all were high. The MODEK bit in the keyboard status and
control register controls the triggering mode of the keyboard interrupt.
• If the keyboard interrupt is edge-sensitive only, a falling edge on a
keyboard pin does not latch an interrupt request if another
keyboard pin is already low. To prevent losing an interrupt request
on one pin because another pin is still low, software can disable
the latter pin while it is low.
• If the keyboard interrupt is falling edge- and low level-sensitive, an
interrupt request is present as long as any keyboard pin is low.
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:
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 — Rev. 1.0
MOTOROLA
Keyboard Interrupt Module (KBI)
Technical Data
173