R8C2K datasheet(101/471 Pages) RENESAS

101 / 471 page

R8C/2K Group, R8C/2L Group

10. Clock Generation Circuit

Rev.1.10

Dec 21, 2007

Page 84 of 450

REJ09B0406-0110

10.4

Power Control

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

operating mode.

10.4.1

Standard Operating Mode

Standard operating mode is further separated into four modes.

In standard 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 needs to be oscillating

and stable. If the new clock source is the XIN clock, allow sufficient wait time in a program until oscillation is

stabilized before exiting.

−: can be 0 or 1, no change in outcome

Table 10.2

Settings and Modes of Clock Associated Bits

Modes

OCD Register

CM1 Register

CM0 Register

FRA0 Register

OCD2

CM17, CM16

CM14

CM13

CM06

CM05

FRA01 FRA00

High-speed

clock mode

No division

00b

−

−−

Divide-by-2

01b

−

−−

Divide-by-4

10b

−

−−

Divide-by-8

−−

Divide-by-16

11b

−

−−

High-speed

on-chip

oscillator

mode

No division

00b

−−

−

Divide-by-2

01b

−−

−

Divide-by-4

10b

−−

−

Divide-by-8

−−

−

Divide-by-16

11b

−−

−

Low-speed

on-chip

oscillator

mode

No division

00b

−

Divide-by-2

01b

−

Divide-by-4

10b

−

Divide-by-8

−

Divide-by-16

11b

−

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