M30620FCAFP datasheet(533/615 Pages) RENESAS

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Controlling Power Applications

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

2-216

3.8 Controlling Power Using Wait Mode

The following are steps for controling power using wait mode. Figure 3.8.1 shows the operation

timing, and Figures 3.8.2 to 3.8.4 show the set-up procedure.

Use the following peripheral functions:

• Timer mode of timer B

• Wait mode

A flag named “F-WIT” is used in the set-up procedure. The purpose of this flag is to decide

whether or not to clear wait mode. If F_WIT = “1” in the main program, the wait mode is entered;

if F_WIT = “0”, the wait mode is cleared.

(1) Connect a 32.768-kHz oscillator to XCIN to serve as the timer count source. As interrupts

occur every one second, which is a count the timer reaches, the controller returns from wait

mode and count the clock using a program.

________

(2) Clear wait mode if a INT0 interrupt request occurs.

(1) Switch the system clock from XIN to XCIN to get low-speed mode.

_______

(2) Stop XIN and enter wait mode. In this instance, enable the timer B2 interrupt and the INT0 interrupt.

(3) When a timer B2 interrupt request occurs (at 1-second intervals), start supplying the BCLK

from XCIN.

At this time, count the clock within the routine that handles the timer B2 interrupts and enter wait

mode again.

_______

(4) If a INT0 interrupt occurs, start supplying the BCLK from XCIN. Start the XIN oscillation within

_______

the INT0 interrupt, and switch the system clock to XIN.

Overview

Specifications

Operation

Timer B2

interrupt processing

Timer B2 overflow

XCIN

XOUT

BCLK

INT0

(1) Shift to low-speed mode

(2) Stop XIN

(3) Timer B2 interrupt

(4) INT0 interrupt

“H”

“L”

High-speed

Low-speed

High-speed

Figure 3.8.1. Operation timing of controling power using wait mode

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