R8CSLASH15 datasheet(60/277 Pages) RENESAS

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R8C/14 Group, R8C/15 Group

9. Clock Generation Circuit

Rev.2.10

Jan 19, 2006

Page 48 of 253

REJ09B0164-0210

9.4

Power Control

There are three power control modes. All modes other than wait and stop modes are referred to as

normal operating mode.

9.4.1

Normal Operating Mode

Normal operating mode is further separated into four modes.

In normal operating mode, the CPU clock and the peripheral function clock are supplied to operate

the CPU and the peripheral function clocks. Power consumption control is enabled by controlling the

CPU clock frequency. The higher the CPU clock frequency, the more processing power increases.

The lower the CPU clock frequency, the more power consumption decreases. When unnecessary

oscillator circuits stop, power consumption is further reduced.

Before the clock sources for the CPU clock can be switched over, the new clock source after

switching needs to be stabilized and oscillated. If the new clock source is the main clock, allow

sufficient wait time in a program until an oscillation is stabilized before exiting.

NOTES:

1. The low-speed on-chip oscillator is used as the on-chip oscillator clock when the CM14 bit in the

CM1 register is set to “0” (low-speed on-chip oscillator on) and the HRA01 bit in the HRA0 register

is set to “0”. The high-speed on-chip oscillator is used as the on-chip oscillator clock when the

HRA00 bit in the HRA0 register is set to “1” (high-speed on-chip oscillator A on) and the HRA01 bit

in the HRA0 register is set to “1”.

Table 9.2

Setting and Mode of Clock Associated Bit

Modes

OCD Register

CM1 Register

CM0 Register

OCD2

CM17, CM16

CM13

CM06

CM05

High-Speed Mode

00b

Medium-

Speed

Mode

divide-by-2

01b

divide-by-4

10b

divide-by-8

−

divide-by-16

11b

High-Speed,

Low-Speed

On-Chip

Oscillator

Mode(1)

no division

00b

−

divide-by-2

01b

−

divide-by-4

10b

−

divide-by-8

−−

−

divide-by-16

11b

−

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