M306H7MG-XXXFP Datasheet, PDF (33/329 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with DATA ACQUISITION CONTROLLER

M306H7MG-XXXFP/MC-XXXFP/FGFP
4. CLOCK GENERATION CIRCUIT
4.2 CPU Clock and Peripheral Function Clock
Two type clocks: CPU clock to operate the CPU and peripheral function clocks to operate the peripheral functions.
4.2.1 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 sub clock.
If the main clock is selected as the clock source for the CPU clock, the selected 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.
When the level on the STARTB pin is “H”, the main clock divided by 8 provides the CPU clock after reset.
When the level on the STARTB pin is “L”, the sub clock of frequency divided by 8 provides the CPU clock
after reset.
At this time, the CM04 bit and the CM05 bit of CM0 register become “1” .
Note that when entering stop mode from high or middle speed mode, or when the CM05 bit of CM0 register is
set to “1” (main clock turned off) in low-speed mode, the CM06 bit of CM0 register is set to “1” (divide-by-8
mode).
4.2.2 Peripheral Function Clock(f1, f2, f8, f32, f1SIO, f2SIO, f8SIO, f32SIO, fAD, fC32)
These are operating clocks for the peripheral functions.
Of these, fi (i = 1, 2, 8, 32) and fiSIO are derived from the main clock by dividing them by i. The clock fi is used
for timers A and B, and fiSIO is used for serial I/O. The f8 and f32 clocks can be output from the CLKOUT pin.
The fAD clock is produced from the main clock, and is used for the A/D converter.
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, fiSIO
and fAD clocks are turned off.
The fC32 clock is produced from the sub clock, and is used for timers A and B. This clock can be used when the
sub clock is on.
4.3 Clock Output Function
During single-chip mode, the f8, f32 or fC clock can be output from the CLKOUT pin. Use the CM01 to CM00 bits of
CM0 register to select.
Rev.2.10 Oct 25, 2006 Page 33 of 326
REJ03B0152-0210