M16C80 Datasheet, PDF (64/358 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/80 SERIES

M16C/80 Group
8. Clock Generating Circuit
8.7 Power Saving
In Power Save modes, the CPU and oscillator stop and the operating clock is slowed to minimize power
dissipation by the CPU. The following outlines the Power Save modes.
There are three power save modes.
(1) Normal operating mode
• High-speed mode
In this mode, one main clock cycle forms BCLK. The CPU operates on the selected internal clock. The
peripheral functions operate on the clocks specified for each respective function.
• Medium-speed mode
In this mode, the main clock is divided into 2, 3, 4, 6, 8, 10, 12, 14, or 16 to form BCLK. The CPU
operates on the selected internal clock. The peripheral functions operated on the clocks specified for
each respective function.
• Low-speed mode
In this mode, fc forms BCLK. The CPU operates on the fc clock. fc is the clock supplied by the
subclock. The peripheral functions operate on the clocks specified for each respective function.
• Low power-dissipation mode
This mode is selected when the main clock is stopped from low-speed mode. The CPU operates on
the fc clock. fc is the clock supplied by the subclock. Only the peripheral functions for which the
subclock was selected as the count source continue to run.
(2) Wait mode
CPU operation is halted in this mode. The oscillator continues to run.
(3) Stop mode
All oscillators stop in this mode. The CPU and internal peripheral functions all stop. Of all 3 power saving
modes, power savings are greatest in this mode.
Figure 8.7 shows the clock transition between each of the three modes, (1), (2), and (3).
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