mc68hc908gr8a Freescale Semiconductor, Inc, mc68hc908gr8a Datasheet - Page 99

• Manufacturer Part Number: mc68hc908gr8a
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 9
Keyboard Interrupt Module (KBI)
9.1 Introduction
The keyboard interrupt module (KBI) provides four independently maskable external interrupts which are
accessible via PTA0–PTA3. When a port pin is enabled for keyboard interrupt function, an internal pullup
device is also enabled on the pin.
9.2 Features
Features include:
9.3 Functional Description
Writing to the KBIE3–KBIE0 bits in the keyboard interrupt enable register independently enables or
disables each port A pin as a keyboard interrupt pin. Enabling a keyboard interrupt pin also enables its
internal pullup device. A low level applied to an enabled keyboard interrupt pin latches a keyboard
interrupt request.
A keyboard interrupt is latched 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 mode of the keyboard interrupt.
Freescale Semiconductor
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Four keyboard interrupt pins with separate keyboard interrupt enable bits and one keyboard
interrupt mask
Hysteresis buffers
Programmable edge-only or edge- and level- interrupt sensitivity
Exit from low-power modes
I/O (input/output) port bit(s) software configurable with pullup device(s) if configured as input port
bit(s)
If the keyboard interrupt 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 latter pin 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 pin is low and the pin is keyboard interrupt enabled.
MC68HC908GR8A • MC68HC908GR4A Data Sheet, Rev. 5
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