MC68HC908GR4MP datasheet(37/286 Pages) FREESCALE

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MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7

Freescale Semiconductor

Chapter 3

Low-Power Modes

3.1 Introduction

The MCU may enter two low-power modes: wait mode and stop mode. They are common to all HC08

MCUs and are entered through instruction execution. This section describes how each module acts in the

low-power modes.

3.1.1 Wait Mode

The WAIT instruction puts the MCU in a low-power standby mode in which the CPU clock is disabled but

the bus clock continues to run. Power consumption can be further reduced by disabling the LVI module

and/or the timebase module through bits in the CONFIG register. (See Chapter 8 Configuration Register

(CONFIG).)

3.1.2 Stop Mode

Stop mode is entered when a STOP instruction is executed. The CPU clock is disabled and the bus clock

is disabled if the OSCSTOPENB bit in the CONFIG register is at a logic 0. (See Chapter 8 Configuration

3.2 Analog-to-Digital Converter (ADC)

3.2.1 Wait Mode

The ADC continues normal operation during wait mode. Any enabled CPU interrupt request from the ADC

can bring the MCU out of wait mode. If the ADC is not required to bring the MCU out of wait mode, power

down the ADC by setting ADCH4–ADCH0 bits in the ADC status and control register before executing the

WAIT instruction.

3.2.2 Stop Mode

The ADC module is inactive after the execution of a STOP instruction. Any pending conversion is aborted.

ADC conversions resume when the MCU exits stop mode after an external interrupt. Allow one

conversion cycle to stabilize the analog circuitry.

MC68HC908GR4MP Datasheet(PDF) 37 Page - Freescale Semiconductor, Inc