MC908GZ60CFUE Datasheet, PDF (115/352 Pages) Freescale Semiconductor, Inc – Standard features, Features of the CPU08

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.
MC68HC908GZ60 • MC68HC908GZ48 • MC68HC908GZ32 Data Sheet, Rev. 6
Freescale Semiconductor
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