Freescale Semiconductor, Inc.
Technical Data — MC68HC11P2
Section 10. Resets and Interrupts
10.1 Contents
10.2 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
10.3 Resets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
10.4 Effects of reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192
10.5 Reset and interrupt priority . . . . . . . . . . . . . . . . . . . . . . . . .195
10.6 Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200
10.7 Low power operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
10.2 Introduction
Resets and interrupt operations load the program counter with a vector
that points to a new location from which instructions are to be fetched. A
reset immediately stops execution of the current instruction and forces
the program counter to a known starting address. Internal registers and
control bits are initialized so that the MCU can resume executing
instructions. An interrupt temporarily suspends normal program
execution whilst an interrupt service routine is being executed. After an
interrupt has been serviced, the main program resumes as if there had
been no interruption.
10.3 Resets
There are four possible sources of reset. Power-on reset (POR) and
external reset share the normal reset vector. The computer operating
properly (COP) reset and the clock monitor reset each has its own
MC68HC11P2 — Rev 1.0
Technical Data
Resets and Interrupts
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