M68HC08 datasheet(43/188 Pages) FREESCALE

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MC68HC908RF2 — Rev. 4.0

Data Sheet

MOTOROLA

Configuration Register (CONFIG)

Data Sheet — MC68HC908RF2

Section 3. Configuration Register (CONFIG)

3.1 Introduction

This section describes the configuration register (CONFIG). The configuration

•

Stop mode recovery time (32 CGMXCLK cycles or 4,096 CGMXCLK cycles)

•

COP timeout period (218 – 24 or 213 – 24 CGMXCLK cycles)

•STOP instruction

•

Computer operating properly module (COP)

•

Low-voltage inhibit (LVI) module control

3.2 Functional Description

The CONFIG register is used in the initialization of various options and can be

written once after each reset. The register is set to the documented value during

reset. Since the various options affect the operation of the MCU, it is recommended

that these registers be written immediately after reset. The configuration register is

located at $001F.

NOTE:

On a FLASH device, the options are one-time writable by the user after each reset.

The CONFIG register is not in the FLASH memory but is a special register

containing one-time writable latches after each reset. Upon a reset, the CONFIG

EXTSLOW — Slow External Crystal Enable Bit

The EXTSLOW bit has two functions. It configures the ICG module for a fast

(1 MHz–8 MHz) or slow (30 kHz–100 kHz) speed crystal. The option also

configures the clock monitor operation in the ICG module to expect an external

Address: $001F

BIt 7

654321

Bit 0

Read:

EXTSLOW

LVISTOP

LVIRST

LVIPWR

COPRS

SSREC

STOP

COPD

Write:

Reset:

0110000

Figure 3-1. Configuration Register (CONFIG)

Freescale Semiconductor, Inc.

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