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Power Control

M30240 Group

Rev.1.00 Sep 24, 2003 Page 275 of 360

2.12 Power Control

2.12.1 Overview

‘Power Control’ refers to the reduction of CPU power consumption by stopping the CPU and oscillators,

or decreasing the operation clock. The following is a description of the three available power control

modes:

2.12.1.1 Modes

Power control is available in three modes.

(a) Normal operation mode

• High-speed mode

Divide-by-1 frequency of the main clock becomes the internal clock Φ. Each peripheral function operates ac-

cording to its assigned clock.

• Medium-speed mode

Divide-by-2, divide-by-4, divide-by-8, or divide-by-16 frequency of the main clock becomes the internal clock

Φ. The CPU operates according to the internal clock Φ selected. Each peripheral function operates according

to its assigned clock.

(b) Wait mode

The CPU operation is stopped. The oscillators do not stop.

All oscillators stop. The CPU and all built-in peripheral functions stop. This mode, among the three modes list-

ed here, is the most effective in decreasing power consumption.

Figure 2.124 is the state transition diagram of the above modes.

Figure 2.124: State transition diagram of power control modes

Note 1: Change CM06 after cnaging CM16 and CM17

Note2: Switch clock after oscillation of main clock is stable.

2.12.1.2 Switching the driving capacity of the oscillation circuit

The main clock has the ability to switch its’ drive capacity. Reducing the drive capacity after the

oscillation stabilizes allows for further reduction in power consumption.

2.12.1.3 Clearing stop mode and wait mode

The stop mode and wait mode can be cleared by generating an interrupt request, or by resetting the

hardware. Set the priority level of the interrupt (to clear these modes) higher than the processor interrupt

CPU operation stopped

All oscillators stopped

Stop Mode

All oscillators stopped

Medium-speed mode

(divided-by-8 mode)

RESET

High-speed/medium-

speed mode

Normal Mode

WAIT

instruction

Interrupt

WAIT

instruction

Interrupt

CM10 = "1"

Interrupt

Wait Mode

CM06 = "1"

(Note 1)

CM06 = "0"

(Notes 1, 2)

Note 1: Change CM06 after changing CM16 and CM17.

Note 2: Switch clock after main clock oscillation is stable.

Brand	Renesas
Model	M16C Series
Category	Computer Hardware
Language	English

Renesas M16C Series User Manual

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Renesas M16C Series Specifications

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