MC68HC908QL4 Datasheet, PDF (89/226 Pages) Motorola, Inc – Microcontrollers

Chapter 9
Keyboard Interrupt Module (KBI)
9.1 Introduction
The keyboard interrupt module (KBI) provides independently maskable external interrupts.
The KBI shares its pins with general-purpose input/output (I/O) port pins. See Figure 9-1 for port location
of these shared pins.
9.2 Features
Features of the keyboard interrupt module include:
• Keyboard interrupt pins with separate keyboard interrupt enable bits and one keyboard interrupt
mask
• Programmable edge-only or edge and level interrupt sensitivity
• Edge sensitivity programmable for rising or falling edge
• Level sensitivity programmable for high or low level
• KBI can be configured to use either internal or external pullup/pulldown devices using PTAPUE,
see 12.3.3 Port A Input Pullup/Down Enable Register
– When in internal device is enabled, pullup or pulldown device automatically configured based
on the polarity of edge or level detect
• Exit from low-power modes
9.3 Functional Description
The keyboard interrupt module controls the enabling/disabling of interrupt functions on the KBI pins.
These pins can be enabled/disabled independently of each other. See Figure 9-2.
9.3.1 Keyboard Operation
Writing to the KBIEx bits in the keyboard interrupt enable register (KBIER) independently enables or
disables each KBI pin. The polarity of the keyboard interrupt is controlled using the KBIPx bits in the
keyboard interrupt polarity register (KBIPR). Edge-only or edge and level sensitivity is controlled using the
MODEK bit in the keyboard status and control register (KBISCR).
Enabling a keyboard interrupt pin also enables its internal pullup or pulldown device based on the polarity
enabled and the corresponding port pullup/down enable bit, PTAPUEx see 12.3.3 Port A Input
Pullup/Down Enable Register. On falling edge or low level detection, a pullup device is configured. On
rising edge or high level detection, a pulldown device is configured.
MC68HC908QL4 Data Sheet, Rev. 7
Freescale Semiconductor
89