R8CSLASH2G datasheet(118/344 Pages) RENESAS

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R8C/2G Group

11. Clock Generation Circuit

Rev.1.00

Apr 04, 2008

Page 98 of 318

REJ09B0387-0100

11.3

CPU Clock and Peripheral Function Clock

There are a CPU clock to operate the CPU and a peripheral function clock to operate the peripheral functions. Refer

to Figure 11.1 Clock Generation Circuit.

11.3.1

System Clock

The system clock is the clock source for the CPU and peripheral function clocks. Either the XCIN clock or the

on-chip oscillator clock can be selected.

11.3.2

CPU Clock

The CPU clock is an operating clock for the CPU and watchdog timer.

The system clock can be divided by 1 (no division), 2, 4, 8, or 16 to produce the CPU clock. Use the CM06 bit

in the CM0 register and bits CM16 to CM17 in the CM1 register to select the value of the division.

Use the XCIN clock while the XCIN clock oscillation stabilizes.

After reset, the low-speed on-chip oscillator clock divided by 8 provides the CPU clock.

When entering stop mode from high-speed clock mode, the CM06 bit is set to 1 (divide-by-8 mode).

11.3.3

Peripheral Function Clock (f1, f2, f4, f8, and f32)

The peripheral function clock is the operating clock for the peripheral functions.

The clock fi (i = 1, 2, 4, 8, and 32) is generated by the system clock divided by i. The clock fi is used for timers

RA, RB, RE, and RF, and the serial interface.

When the WAIT instruction is executed after setting the CM02 bit in the CM0 register to 1 (peripheral function

clock stops in wait mode), the clock fi stop.

11.3.4

fOCO

fOCO is an operating clock for the peripheral functions.

fOCO runs at the same frequency as the on-chip oscillator clock and can be used as the source for timer RA.

When the WAIT instruction is executed, the clocks fOCO does not stop.

11.3.5

fOCO-F

fOCO-F is generated by the high-speed on-chip oscillator and supplied by setting the HRA00 bit to 1.

When the WAIT instruction is executed, the clock fOCO-F does not stop.

11.3.6

fOCO-S

fOCO-S is an operating clock for the watchdog timer and voltage detection circuit. fOCO-S is supplied by

setting the CM14 bit to 0 (low-speed on-chip oscillator on) and uses the clock generated by the low-speed on-

chip oscillator. When the WAIT instruction is executed or in count source protect mode of the watchdog timer,

fOCO-S does not stop.

11.3.7

fC4 and fC32

The clock fC4 is used for timer RE and the clock fC32 is used for timer RA, timer RF, and watchdog timer.

Use fC4 and fC32 while the XCIN clock oscillation stabilizes.

R8C/2G 数据表(PDF) 118 Page - Renesas Technology Corp

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