mc908jl16 Freescale Semiconductor, Inc, mc908jl16 Datasheet - Page 151

• Manufacturer Part Number: mc908jl16
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 11
External Interrupt (IRQ)
11.1 Introduction
The external interrupt (IRQ) module provides a maskable interrupt input.
11.2 Features
Features of the IRQ module include the following:
11.3 Functional Description
A logic zero applied to the external interrupt pin can latch a CPU interrupt request.
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:
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 the interrupt pin is edge-triggered only, the CPU interrupt request remains set until a vector fetch,
software clear, or reset occurs.
When the interrupt pin is both falling-edge and low-level-triggered, the CPU interrupt request remains set
until both of the following 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
Selectable internal pullup resistor
Vector fetch — A vector fetch automatically generates an interrupt acknowledge signal that clears
the IRQ latch.
Software clear — Software can clear the interrupt latch by writing to the acknowledge bit in the
interrupt status and control register (INTSCR). Writing a logic one 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 one
MC68HC908JL16 Data Sheet, Rev. 1.1
Figure 11-1
shows the
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