MC68HC908GR16 Datasheet, PDF (109/310 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Data Sheet — MC68HC908GR16
Section 9. Keyboard Interrupt Module (KBI)
9.1 Introduction
The keyboard interrupt module (KBI) provides eight independently maskable
external interrupts which are accessible via PTA0–PTA7. 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:
• Eight 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)
9.3 Functional Description
Writing to the KBIE7–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 logic 0
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.
• 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.
MC68HC908GR16 — Rev. 1.0
MOTOROLA
Keyboard Interrupt Module (KBI)
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Data Sheet
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