M16CSLASH62M datasheet(490/615 Pages) RENESAS

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Power Control

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

2-173

2.15 Power Control Usage

2.15.1 Overview of the power control usage

‘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:

(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 BCLK. The CPU operates with the BCLK

selected. Each peripheral function operates according 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

BCLK. The CPU operates according to the BCLK selected. Each peripheral function operates

according to its assigned clock.

• Low-speed mode

fC becomes the BCLK. The CPU operates according to the fc clock. The fC clock is supplied by the

secondary clock. Each peripheral function operates according to its assigned clock.

• Low power consumption mode

The main clock operating in low-speed mode is stopped. The CPU operates according to the fc

clock. The fc clock is supplied by the secondary clock. The only peripheral functions that operate

are those with the sub-clock selected as the count source.

(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 listed here, is the most effective in decreasing power consumption.

Figure 2.15.1 is the state transition diagram of the above modes.

(2) Switching the driving capacity of the oscillation circuit

Both the main clock and the secondary clock have the ability to switch the driving capacity. Reducing

the driving capacity after the oscillation stabilizes allows for further reduction in power consumption.

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