參數(shù)資料
型號: MC68HC08GP8AMFB
廠商: FREESCALE SEMICONDUCTOR INC
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 8.2 MHz, MICROCONTROLLER, PQFP44
封裝: PLASTIC, QFP-44
文件頁數(shù): 124/126頁
文件大小: 4243K
代理商: MC68HC08GP8AMFB
Keyboard Interrupt (KBI) Module
Keyboard Initialization
MC68HC08GP8A
Data Sheet
MOTOROLA
Keyboard Interrupt (KBI) Module
97
8.4 Keyboard Initialization
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:
1.
Mask keyboard interrupts by setting the IMASKK bit in the keyboard status
and control register.
2.
Enable the KBI pins by setting the appropriate KBIEx bits in the keyboard
interrupt enable register.
3.
Write to the ACKK bit in the keyboard status and control register to clear any
false interrupts.
4.
Clear the IMASKK bit.
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.
Configure the keyboard pins as outputs by setting the appropriate DDRA
bits in data direction register A.
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 keyboard
interrupt enable register.
8.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby
modes.
8.5.1 Wait Mode
The keyboard module remains active in wait mode. Clearing the IMASKK bit in the
keyboard status and control register enables keyboard interrupt requests to bring
the MCU out of wait mode.
8.5.2 Stop Mode
The keyboard module remains active in stop mode. Clearing the IMASKK bit in the
keyboard status and control register enables keyboard interrupt requests to bring
the MCU out of stop mode.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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