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MC68HC705C9A — Rev. 2.0

Interrupts

General Release Specification — MC68HC705C9A

Section 4. Interrupts

4.1 Contents

4.2

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45

4.3

Non-Maskable Software Interrupt (SWI). . . . . . . . . . . . . . . . . .47

4.4

External Interrupt (IRQ or Port B) . . . . . . . . . . . . . . . . . . . . . . .47

4.5

Timer Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48

4.6

SCI Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48

4.7

SPI Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48

4.2 Introduction

The MCU can be interrupted by five different sources, four maskable

hardware interrupts, and one non-maskable software interrupt:

•

External signal on the IRQ pin or port B pins

•

16-bit programmable timer

•

Serial communications interface

•

Serial peripheral interface

•

Software interrupt instruction (SWI)

Interrupts cause the processor to save register contents on the stack

and to set the interrupt mask (I bit) to prevent additional interrupts. The

RTI instruction causes the register contents to be recovered from the

stack and normal processing to resume.

Unlike RESET, hardware interrupts do not cause the current instruction

execution to be halted, but are considered pending until the current

instruction is complete.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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