s908gr32ag3vfa Freescale Semiconductor, Inc, s908gr32ag3vfa Datasheet - Page 109

• Manufacturer Part Number: s908gr32ag3vfa
• 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
8.3 Functional Description
A low applied to the external interrupt pin can latch a central processor unit (CPU) interrupt request.
Figure 8-1
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 an interrupt pin is edge-triggered only (MODE = 0), 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 (MODE = 1), the interrupt remains set
until both of these events occur:
Freescale Semiconductor
•
•
•
•
•
•
•
•
•
•
•
•
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
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 a high level
shows the structure of the IRQ module.
MC68HC908GR60A • MC68HC908GR48A • MC68HC908GR32A Data Sheet, Rev. 5
109