Keyboard Interrupt Module (KBI)
Functional Description
MC68HC908QF4 — Rev. 1.0
Data Sheet
MOTOROLA
Keyboard Interrupt Module (KBI)
81
Figure 9-3. Keyboard Interrupt Block Diagram
9.3 Functional Description
The keyboard interrupt module controls the enabling/disabling of interrupt
functions on the six port A pins. These six pins can be enabled/disabled
independently of each other.
9.3.1 Keyboard Operation
Writing to the KBIE0–KBIE5 bits in the keyboard interrupt enable register (KBIER)
independently enables or disables each port A pin as a keyboard interrupt pin.
Enabling a keyboard interrupt pin in port A also enables its internal pullup device
irrespective of PTAPUEx bits in the port A input pullup enable register (see
keyboard interrupt pin latches a keyboard interrupt request.
A keyboard interrupt is latched when one or more keyboard interrupt inputs 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
interrupt input does not latch an interrupt request if another keyboard pin is
already low. To prevent losing an interrupt request on one input because
another input is still low, software can disable the latter input 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 interrupt input is low.
KBIE0
KBIE5
.
DQ
CK
CLR
VDD
MODEK
IMASKK
KEYBOARD
INTERRUPT FF
VECTOR FETCH
DECODER
ACKK
INTERNAL BUS
RESET
KBI5
KBI0
SYNCHRONIZER
KEYF
KEYBOARD
INTERRUPT
REQUEST
TO PULLUP ENABLE
AWUIREQ(1)
TO PULLUP ENABLE
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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