SC9RS08KA2 datasheet(35/134 Pages) FREESCALE

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SC9RS08KA2 Series Data Sheet, Rev. 1

Freescale Semiconductor

Chapter 5

Resets, Interrupts, and General System Control

5.1

Introduction

This chapter discusses basic reset and interrupt mechanisms and the various sources of reset and interrupt

in the SC9RS08KA2 Series. Some interrupt sources from peripheral modules are discussed in greater

detail within other chapters of this data sheet. This chapter gathers basic information about all reset and

interrupt sources in one place for easy reference. A few reset and wakeup sources, including the computer

operating properly (COP) watchdog and real-time interrupt (RTI), are not part of on-chip peripheral

systems with their own chapters but are part of the system control logic.

5.2

Features

Reset and interrupt features include:

•

Multiple sources of reset for flexible system configuration and reliable operation

•

System reset status register (SRS) to indicate the source of the most recent reset

•

System interrupt pending register (SIP1) to indicate the status of pending system interrupts

— Analog comparator interrupt with enable

— Keyboard interrupt with enable

— Low-voltage detect interrupt with enable

— Modulo timer interrupt with enable

— Real-time interrupt with enable; available in stop with multiple rates based on a separate 1-kHz

self-clocked source

5.3

MCU Reset

Resetting the MCU provides a way to start processing from a known set of initial conditions. During reset,

most control and status registers are forced to initial values and the program counter is started from

location $3FFD. A JMP instruction (opcode $BC) with operand located at $3FFE–$3FFF must be

programmed into the user application for correct reset operation. The operand defines the location at which

the user program will start. On-chip peripheral modules are disabled and I/O pins are initially configured

as general-purpose high-impedance inputs with pullup/pulldown devices disabled.

The SC9RS08KA2 Series has seven sources for reset:

•

External pin reset (PIN) — enabled using RSTPE in SOPT

•

Power-on reset (POR)

•

Low-voltage detect (LVD)

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