mc68hc908gt8 Freescale Semiconductor, Inc, mc68hc908gt8 Datasheet - Page 101

• Manufacturer Part Number: mc68hc908gt8
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 8
External Interrupt (IRQ)
8.1 Introduction
The IRQ (external interrupt) module provides a maskable interrupt input.
8.2 Features
Features of the IRQ module include:
8.3 Functional Description
A logic 0 applied to the external interrupt pin can latch a central processor unit (CPU) interrupt request.
Figure 8-2
Interrupt signals on the IRQ pin are latched into the IRQ latch. An interrupt latch remains set until one of
the following actions occurs:
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.
When an interrupt pin is both falling-edge and low-level triggered, the interrupt remains set until both of
these events occur:
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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
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 1 to the ACK bit clears the IRQ
latch.
Reset — A reset automatically clears the interrupt latch.
Vector fetch or software clear
Return of the interrupt pin to logic 1
shows the structure of the IRQ module.
MC68HC908GT16 • MC68HC908GT8 • MC68HC08GT16 Data Sheet, Rev. 5.0
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