MC68HC908KX2 MOTOROLA [Motorola, Inc], MC68HC908KX2 Datasheet - Page 173

• Manufacturer Part Number: MC68HC908KX2
• Description: Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

13.4 Functional Description
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 — Rev. 1.0
MOTOROLA
Addr.
$001A
$001B
Keyboard Interrupt Enable
Control Register (KBSCR)
Register Name
Keyboard Status and
Register (KBIER)
See page 177.
See page 178.
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 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:
Reset:
Reset:
Read:
Read:
Write:
Write:
•
•
Figure 13-2. I/O Register Summary
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.
Bit 7
0
0
0
0
Keyboard Interrupt Module (KBI)
= Unimplemented
6
0
0
0
0
5
0
0
0
0
KBIE4
4
0
0
0
KBIE3
KEYF
3
0
0
Keyboard Interrupt Module (KBI)
KBIE2
ACKK
2
0
0
0
Functional Description
IMASKK
KBIE1
1
0
0
Technical Data
MODEK
KBIE0
Bit 0
0
0
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