MC68HC08AZ0 Datasheet, PDF (322/444 Pages) Motorola, Inc – Advance Information

Freescale Semiconductor, Inc.
Keyboard Module (KB)
Functional description
Writing to the KBIE4–KBIE0 bits in the keyboard interrupt enable register
independently enables or disables each port G or port H pin as a
keyboard interrupt pin. Enabling a keyboard interrupt pin also enables its
pull-up device. A logic zero applied to a keyboard interrupt pin can latch
a keyboard interrupt request.
The keyboard interrupt latch becomes set 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 sensitivity of the keyboard
interrupt latch.
• If the keyboard interrupt latch 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 former pin while it is low.
• If the keyboard interrupt latch is edge- and level-sensitive, an
interrupt request is latched as long as any keyboard pin is low.
PTG4/
KBD4
To pullup
enable
KB4IE
PTG0/
KBD0
To pullup
enable
KB0IE
MC68HC08AZ0
320
INTERNAL BUS
V_DD
D ^CLR Q
CK
ACKK
VECTOR FETCH
DECODER
KEYBOARD
INTERRUPT
LATCH
IMASKK
SYNCHRONIZER
KEYBOARD
INTERRUPT
REQUEST
MODEK
Figure 5. Keyboard module block diagram
Keyboard Module (KB)
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2-kbd
MOTOROLA