Datasheet

M16C/6S Group Clock Generation Circuit
R01DS0201EJ0502 Rev.5.02 page 35 of 203
Dec 25, 2012
CPU Clock and Peripheral Function Clock
Two type clocks: CPU clock to operate the CPU and peripheral function clocks to operate the peripheral
functions.
(1) CPU Clock and BCLK
These are operating clocks for the CPU and watchdog timer.
The clock source for the CPU clock can be chosen to be the main clock, or On-chip Oscillator clock.
If the main clock or On-chip Oscillator clock is selected as the clock source for the CPU clock, the se-
lected clock source can be divided by 1 (undivided), 2, 4, 8 or 16 to produce the CPU clock. Use the CM06
bit in CM0 register and the CM17 to CM16 bits in CM1 register to select the divide-by-n value.
After reset, the main clock divided by 8 provides the CPU clock.
Note that when entering stop mode from high or middle speed mode or On-chip Oscillator mode, the
CM06 bit of CM0 register is set to “1” (divide-by-8 mode).
(2) Peripheral Function Clock(f1, f2, f8, f32, f1SIO, f2SIO, f8SIO, f32SIO)
These are operating clocks for the peripheral functions.
Of these, fi (i = 1, 2, 8, 32) and fiSIO are derived from the main clock, or On-chip Oscillator clock by dividing
them by i. The clock fi is used for timers A, and fiSIO is used for serial I/O.
When the WAIT instruction is executed after setting the CM02 bit of CM0 register to “1” (peripheral
function clock turned off during wait mode), or when the microcomputer is in low power dissipation mode,
the fi, and fiSIO clocks are turned off.