Datasheet

Table Of Contents
MC68HC908GR60A • MC68HC908GR48A • MC68HC908GR32A Data Sheet, Rev. 5
Freescale Semiconductor 113
Chapter 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/pulldown 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
Edge detect programmable for rising or falling edges
Level detect programmable for high or low levels
Exit from low-power modes
Pullup/pulldown device automatically configured based on polarity of edge/level selection
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/pulldown device. On falling edge or low level selection a pullup device is configured. On
rising edge or high level selection a pulldown device is configured.
A falling edge is detected when an enabled keyboard input signal is seen as a 1 (the deasserted
level) during one bus cycle and then a 0 (the asserted level) during the next cycle.
A rising edge is detected when the input signal is seen as a 0 during one bus cycle and then a 1
during the next cycle.
A keyboard interrupt is latched when one or more keyboard pins are asserted. The MODEK bit in the
keyboard status and control register controls the triggering mode of the keyboard interrupt.