MC68HC908GR4MP datasheet(89/286 Pages) FREESCALE

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MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7

Freescale Semiconductor

Chapter 8

Configuration Register (CONFIG)

8.1 Introduction

This section describes the configuration registers, CONFIG1 and CONFIG2. The configuration registers

enable or disable these options:

•

Stop mode recovery time (32 CGMXCLK cycles or 4096 CGMXCLK cycles)

•

COP timeout period (262,128 or 8176 CGMXCLK cycles)

•STOP instruction

•

Computer operating properly module (COP)

•

Low-voltage inhibit (LVI) module control and voltage trip point selection

•

Enable/disable the oscillator (OSC) during stop mode

8.2 Functional Description

The configuration registers are used in the initialization of various options. The configuration registers can

be written once after each reset. All of the configuration register bits are cleared 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 registers are located at $001E and $001F. The configuration

NOTE

To ensure correct operation of the MCU under all operating conditions, the user must write data $1C to

address $0033 immediately after reset. This is to ensure proper termination of an unused module within

the MCU.

NOTE

On a FLASH device, the options except LVI5OR3 are one-time writeable by

the user after each reset. The LVI5OR3 bit is one-time writeable by the user

only after each POR (power-on reset). The CONFIG registers are not in the

FLASH memory but are special registers containing one-time writeable

latches after each reset. Upon a reset, the CONFIG registers default to

predetermined settings as shown in Figure 8-1 and Figure 8-2.

Address:

$001E

Bit 7

654321

Bit 0

Read:

000000

OSC-

STOPENB

SCIBD-

SRC

Write:

Reset:

00000000

= Unimplemented

Figure 8-1. Configuration Register 2 (CONFIG2)

MC68HC908GR4MP Datasheet(PDF) 89 Page - Freescale Semiconductor, Inc

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