4556 datasheet(57/145 Pages) RENESAS

57 / 145 page

Rev.3.02

Dec 22, 2006

page 57 of 142

REJ03B0025-0302

4556 Group

CLOCK CONTROL

The clock control circuit consists of the following circuits.

• On-chip oscillator (internal oscillator)

• Ceramic resonator

• RC oscillation circuit

• Quartz-crystal oscillation circuit

• Multi-plexer (clock selection circuit)

• Frequency divider

• Internal clock generating circuit

Fig. 47 Clock control circuit structure

The system clock and the instruction clock are generated as the

source clock for operation by these circuits.

Figure 47 shows the structure of the clock control circuit.

The 4556 Group operates by the on-chip oscillator clock (f(RING))

which is the internal oscillator after system is released from reset.

Also, the ceramic resonator or the RC oscillation can be used for

the main clock (f(XIN)) of the 4556 Group.

The quartz-crystal oscillator can be used for sub-clock (f(XCIN)).

MR3, MR2

CRCK instruction

Q S

Internal reset signal

Key-on wakeup signal

EPOF instruction

POF2 instruction

XCOUT

XCIN

EPOF instruction

POF instruction

T3F signal

MR1, MR0

System clock (STCK)

Instruction clock

(INSTCK)

Multi-

plexer

Quartz-crystal

oscillation

On-chip oscillator

(internal oscillator)

XOUT

XIN

Ceramic

resonance

RC oscillation

Internal clock

generating circuit

(divided by 3)

RG1

RG0

RG2

Divided by 2

Divided by 4

Divided by 8

Division circuit

4556 Datasheet(PDF) 57 Page - Renesas Technology Corp

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