MC68HC908AB32 MOTOROLA [Motorola, Inc], MC68HC908AB32 Datasheet - Page 349

• Manufacturer Part Number: MC68HC908AB32
• Description: HCMOS Microcontroller Unit
• Manufacturer: MOTOROLA [Motorola, Inc]

19.5.1 Keyboard Initialization
19.5.2 Keyboard Status and Control Register
MC68HC908AB32
MOTOROLA
—
Rev. 1.0
When a keyboard interrupt pin is enabled, it takes time for the internal
pull-up to reach a logic 1. Therefore a false interrupt can occur as soon
as the pin is enabled.
To prevent a false interrupt on keyboard initialization:
An interrupt signal on an edge-triggered pin can be acknowledged
immediately after enabling the pin. An interrupt signal on an edge- and
level-triggered interrupt pin must be acknowledged after a delay that
depends on the external load.
Another way to avoid a false interrupt:
1. Mask keyboard interrupts by setting the IMASKK bit in the
2. Enable the KBI pins by setting the appropriate KBIEx bits in the
3. Write to the ACKK bit in the keyboard status and control register
4. Clear the IMASKK bit.
1. Configure the keyboard pins as outputs by setting the appropriate
2. Write logic 1s to the appropriate port data register bits.
3. Enable the KBI pins by setting the appropriate KBIEx bits in the
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Freescale Semiconductor, Inc.
For More Information On This Product,
keyboard status and control register.
keyboard interrupt enable register.
to clear any false interrupts.
DDR bits in the data direction register.
keyboard interrupt enable register.
Flags keyboard interrupt requests.
Acknowledges keyboard interrupt requests.
Masks keyboard interrupt requests.
Controls keyboard interrupt triggering sensitivity.
Keyboard Interrupt Module (KBI)
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Keyboard Interrupt Module (KBI)
Functional Description
Technical Data
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