MC68HC908GR8 Datasheet, PDF (121/286 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Chapter 13
Keyboard Interrupt (KBI)
13.1 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.
13.2 Features
• 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)
13.3 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.
INTERNAL BUS
KBD0
TO PULLUP
.
ENABLE
.
KB0IE
.
KBD3
TO PULLUP
ENABLE
KB3IE
Freescale Semiconductor
VDD
CLR
D
Q
CK
ACKK
RESET
VECTOR FETCH
DECODER
KEYF
SYNCHRONIZER
KEYBOARD
INTERRUPT FF
IMASKK
MODEK
KEYBOARD
INTERRUPT
REQUEST
Figure 13-1. Keyboard Module Block Diagram
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
121