R8C2C datasheet(117/615 Pages) RENESAS

117 / 615 page

R8C/2C Group, R8C/2D Group

10. Clock Generation Circuit

Rev.2.00

Dec 05, 2007

Page 96 of 585

REJ09B0339-0200

10. Clock Generation Circuit

The clock generation circuit has:

• XIN clock oscillation circuit

• XCIN clock oscillation circuit

• Low-speed on-chip oscillator

• High-speed on-chip oscillator

Table 10.1 lists Specifications of Clock Generation Circuit. Figure 10.1 shows a Clock Generation Circuit. Figure 10.2

shows a Peripheral Function Clock. Figures 10.3 to 10.9 show clock associated registers. Figure 10.10 shows a

Procedure for Enabling Reduced Internal Power Consumption Using VCA20 bit.

NOTES:

1. These pins can be used as P4_6 or P4_7 when using the on-chip oscillator clock as the CPU clock while the

XIN clock oscillation circuit is not used.

2. These pins can be used as P4_3 and P4_4 when using the XIN clock oscillation circuit and on-chip oscillator

clock for a CPU clock while the XCIN clock oscillation circuit is not used.

3. Set the CM05 bit in the CM0 register to 1 (XIN clock stopped) and the CM13 bit in the CM1 register to 1 (XIN-

XOUT pin) when an external clock is input.

4. The clock frequency is automatically set to up to 20 MHz by a divider when using the high-speed on-chip

oscillator as the CPU clock source.

Table 10.1

Specifications of Clock Generation Circuit

Item

XIN Clock

Oscillation Circuit

XCIN Clock Oscillation

Circuit

On-Chip Oscillator

High-Speed On-Chip

Oscillator

Low-Speed On-Chip

Oscillator

Applications

• CPU clock source

• Peripheral function

clock source

• CPU clock source

• Timer RA and timer RE

clock source

• CPU clock source

• Peripheral function

clock source

• CPU and peripheral

function clock

sources when XIN

clock stops oscillating

• CPU clock source

• Peripheral function

clock source

• CPU and peripheral

function clock

sources when XIN

clock stops oscillating

Clock frequency 0 to 20 MHz

32.768 kHz

Approx. 40 MHz(4)

Approx. 125 kHz

Connectable

oscillator

• Ceramic resonator

• Crystal oscillator

−−

Oscillator

connect pins

XIN, XOUT(1)

XCIN, XCOUT(2)

−(1)

Oscillation stop,

restart function

Usable

Oscillator status

after reset

Stop

Oscillate

Others

Externally

generated clock can

be input(3)

• Externally generated

clock can be input

• On-chip feedback

resistor Rf (connected/

not connected,

selectable)

−−

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