MC68HC908GR8CDW Freescale Semiconductor, MC68HC908GR8CDW Datasheet - Page 179

• Manufacturer Part Number: MC68HC908GR8CDW
• Description: IC MCU 8K FLASH 8MHZ 28-SOIC
• Manufacturer: Freescale Semiconductor
• Series: HC08r

Specifications of MC68HC908GR8CDW

• Core Processor: HC08
• Core Size: 8-Bit
• Speed: 8MHz
• Connectivity: SCI, SPI
• Peripherals: LVD, POR, PWM
• Number Of I /o: 17
• Program Memory Size: 7.5KB (7.5K x 8)
• Program Memory Type: FLASH
• Ram Size: 384 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 6x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 28-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -

13.5 Keyboard Initialization
MC68HC908GR8 — Rev 4.0
MOTOROLA
NOTE:
Setting a keyboard interrupt enable bit (KBIEx) forces the corresponding
keyboard interrupt pin to be an input, overriding the data direction
register. However, the data direction register bit must be a logic 0 for
software to read the pin.
When a keyboard interrupt pin is enabled, it takes time for the internal
pullup 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 is:
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 A data register bits.
3. Enable the KBI pins by setting the appropriate KBIEx bits in the
Freescale Semiconductor, Inc.
For More Information On This Product,
keyboard status and control register.
keyboard interrupt enable register.
to clear any false interrupts.
DDRA bits in data direction register A.
keyboard interrupt enable register.
Go to: www.freescale.com
Keyboard Interrupt (KBI)
Keyboard Interrupt (KBI)
Keyboard Initialization
Technical Data
179