mc68hc908qf4 Freescale Semiconductor, Inc, mc68hc908qf4 Datasheet - Page 73

• Manufacturer Part Number: mc68hc908qf4
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

8.1 Introduction
8.2 Features
8.3 Functional Description
MC68HC908QF4 — Rev. 1.0
MOTOROLA
Data Sheet — MC68HC908QF4
The IRQ pin (external interrupt), shared with PTA2 (general purpose input) and
keyboard interrupt (KBI), provides a maskable interrupt input.
Features of the IRQ module include the following:
IRQ pin functionality is enabled by setting configuration register 2 (CONFIG2)
IRQEN bit accordingly. A zero disables the IRQ function and IRQ will assume the
other shared functionalities. A one enables the IRQ function.
A falling edge on the external interrupt pin can latch a central processor unit (CPU)
interrupt request.
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 out of reset 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 (MODE = 0), the CPU interrupt
request remains set until a vector fetch, software clear, or reset occurs.
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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 1 to the ACK bit clears the IRQ latch.
Reset — A reset automatically clears the interrupt latch.
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
Figure 8-2
External Interrupt (IRQ)
shows the structure of the IRQ module.
Section 8. External Interrupt (IRQ)
Data Sheet
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