Power Control; Normal Operation Mode - Renesas M16C FAMILY Hardware Manual

Under development
Preliminary specification
Specifications in this manual are tentative and subject to change.
R8C/11 Group

6.4 Power Control

There are three power control modes. For convenience' sake, all modes other than wait and stop modes
are referred to as normal operation mode here.

6.4.1 Normal Operation Mode

Normal operation mode is further classified into three modes.
In normal operation mode, because the CPU clock and the peripheral function clocks both are on, the
CPU and the peripheral functions are operating. Power control is exercised by controlling the CPU
clock frequency. The higher the CPU clock frequency, the greater the processing capability. The lower
the CPU clock frequency, the smaller the power consumption in the chip. If the unnecessary oscillator
circuits are turned off, the power consumption is further reduced.
Before the clock sources for the CPU clock can be switched over, the new clock source to which
switched must be oscillating stably. If the new clock source is the main clock, allow a sufficient wait
time in a program until it becomes oscillating stably.
• High-speed Mode
The main clock divided by 1 (undivided) provides the CPU clock. If the CM14 bit is set to "0" (low-
speed ring oscillator on) or the HR00 bit in the HR0 register is set to "1" (high-speed ring oscillator
on), the f
RING
can be used for timer C.
• Medium-speed Mode
The main clock divided by 2, 4, 8 or 16 provides the CPU clock. If the CM14 bit is set to "0" (low-
speed ring oscillator on) or the HR00 bit in the HR0 register is set to "1" (high-speed ring oscillator
on), the f
RING
can be used for timer C.
• Ring Oscillator Mode
The ring oscillator clock divided by 1 (undivided), 2, 4, 8 or 16 provides the CPU clock. The ring
oscillator clock is also the clock source for the peripheral function clocks. Set the CM06 bit to "1"
(divided by 8 mode) when returning to high-speed and medium-speed. When the HR00 bit is set to
"1", f fast can be used for timer C.
RING-
Rev.0.91 2003 Sep 08
and f can be used for timers Y and C. When the HR00 bit is set to "1", f
RING128
and f can be used for timers Y and C. When the HR00 bit is set to "1", f
RING128
page 36 of 184
6.4 Power Control
fast
RING-
fast
RING-