
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 0 00b 1 0 0
Medium-
Speed
Mode
divide-by-2 0 01b 1 0 0
divide-by-4 0 10b 1 0 0
divide-by-8 0 − 110
divide-by-16 0 11b 1 0 0
High-Speed,
Low-Speed
On-Chip
Oscillator
Mode
(1)
no division 1 00b − 0 −
divide-by-2 1 01b − 0 −
divide-by-4 1 10b − 0 −
divide-by-8 1 −−1 −
divide-by-16 1 11b − 0 −
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