Power Control; Normal Operation Mode; Wait Mode; Stop Mode - Renesas M16C Series User Manual

M30240 Group
• Division by 4 mode
The main clock is divided by 4 to obtain the internal clock Φ.
• Division by 8 mode
The main clock is divided by 8 to obtain the internal clock Φ. Note that oscillation of the main clock
must have stabilized before transferring from this mode to another mode.
• Division by 16 mode
The main clock is divided by 16 to obtain the internal clock Φ.
• No-division mode
The main clock is used as internal clock.
Table 1.8: Operating modes dictated by settings of system clock control registers 0 and 1
CM17 CM16
0 1
1 0
Invalid Invalid
1 1
0 0

1.2.10 Power Control

The following is a description of the three available power control modes:

1.2.10.1 Normal Operation Mode

• High-speed mode
Divide-by-1 frequency of the main clock become the internal clock Φ. The CPU operates with the in-
ternal clock 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 internal
clock Φ. The CPU operates according to the internal clock selected. Each peripheral function operates
according to its assigned clock.

1.2.10.2 Wait mode

The CPU operation is stopped. The oscillators do not stop.

1.2.10.3 Stop Mode

All oscillators stop. The CPU and all built-in peripheral functions stop. Of the three modes listed, this
mode is the most effective in decreasing power consumption.
Rev.1.00 Sep 24, 2003 Page 26 of 360
CM06
0 Division by 2 mode
0 Division by 4 mode
1 Division by 8 mode
0 Division by 16 mode
0 No-division mode
Operating mode of internal clock
Power Control