MC68HC908GZ8 Datasheet, PDF (135/344 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Data Sheet — MC68HC908GZ8
Section 12. External Interrupt (IRQ)
12.1 Introduction
The IRQ (external interrupt) module provides a maskable interrupt input.
12.2 Features
Features of the IRQ module include:
• A dedicated external interrupt pin (IRQ)
• IRQ interrupt control bits
• Hysteresis buffer
• Programmable edge-only or edge and level interrupt sensitivity
• Automatic interrupt acknowledge
• Internal pullup resistor
12.3 Functional Description
A logic 0 applied to the external interrupt pin can latch a central processor unit
(CPU) interrupt request. Figure 12-1 shows the structure of the IRQ module.
Interrupt signals on the IRQ pin are latched into the IRQ latch. An interrupt latch
remains set until one of the following actions occurs:
• Vector fetch — A vector fetch automatically generates an interrupt
acknowledge signal that clears the latch that caused the vector fetch.
• Software clear — Software can clear an interrupt latch by writing to the
appropriate acknowledge bit in the interrupt status and control register
(INTSCR). Writing a logic 1 to the ACK bit clears the IRQ latch.
• Reset — A reset automatically clears the interrupt latch.
The external interrupt pin is falling-edge triggered and is software-configurable to
be either falling-edge or falling-edge and low-level triggered. The MODE bit in the
INTSCR controls the triggering sensitivity of the IRQ pin.
When an interrupt pin is edge-triggered only, the interrupt remains set until a vector
fetch, software clear, or reset occurs.
MC68HC908GZ8
MOTOROLA
External Interrupt (IRQ)
For More Information On This Product,
Go to: www.freescale.com
Data Sheet
135