4524_M datasheet(86/310 Pages) RENESAS

86 / 310 page

4524 Group

HARDWARE

Rev.2.00

Aug, 06 2004

REJ09B0107-0200Z

1-73

Fig. 59 Switch to ceramic oscillation/RC oscillation

Fig. 60 Handling of XIN and XOUT when operating on-chip oscillator

Fig. 61 Ceramic resonator external circuit

Fig. 62 External RC oscillation circuit

Execute the CMCK instruc-

tion in program.

Note: Externally connect a damping

resistor Rd depending on the

oscillation frequency.

(A feedback resistor is built-in.)

Use the resonator manu-

facturer’s recommended value

because constants such as ca-

pacitance depend on the

resonator.

(1) Main clock generating circuit (f(XIN))

The ceramic resonator or RC oscillation can be used for the main

clock of this MCU.

After system is released from reset, the MCU starts operation by

the clock output from the on-chip oscillator which is the internal os-

cillator.

When the ceramic resonator is used, execute the CMCK instruc-

tion. When the RC oscillation is used, execute the CRCK

instruction. The oscillation circuit by the CMCK or CRCK instruction

is valid only at once. The oscillation circuit corresponding to the first

executed one of these two instructions is valid. Other oscillation cir-

cuit and the on-chip oscillator stop.

Execute the CMCK or the CRCK instruction in the initial setting rou-

tine of program (executing it in address 0 in page 0 is

recommended). Also, when the CMCK or the CRCK instruction is

not executed in program, this MCU operates by the on-chip oscilla-

tor.

(2) On-chip oscillator operation

When the MCU operates by the on-chip oscillator as the main clock

(f(XIN)) without using the ceramic resonator or the RC oscillation,

connect XIN pin to VSS and leave XOUT pin open (Figure 60).

The clock frequency of the on-chip oscillator depends on the supply

voltage and the operation temperature range.

Be careful that margin of frequencies when designing application

products.

(3) Ceramic resonator

When the ceramic resonator is used as the main clock (f(XIN)), con-

nect the ceramic resonator and the external circuit to pins XIN and

XOUT at the shortest distance. Then, execute the CMCK instruction.

A feedback resistor is built in between pins XIN and XOUT (Figure

61).

(4) RC oscillation

When the RC oscillation is used as the main clock (f(XIN)), connect

the XIN pin to the external circuit of resistor R and the capacitor C

at the shortest distance and leave XOUT pin open. Then, execute

the CRCK instruction (Figure 62).

The frequency is affected by a capacitor, a resistor and a micro-

computer. So, set the constants within the range of the frequency

limits.

Reset

On-chip oscillator

operation

CMCK instruction

CRCK instruction

• Ceramic resonator valid

• On-chip oscillator stop

• RC oscillation stop

• RC oscillation valid

• On-chip oscillator stop

• Ceramic resonator stop

M34524

XIN

XOUT

Do not use the CMCK instruction

and CRCK instruction in program.

M34524

XIN

XOUT

CIN

COUT

M34524

XIN

XOUT

Execute the CRCK

instruction in program.

FUNCTION BLOCK OPERATIONS

4524_M Datasheet(PDF) 86 Page - Renesas Technology Corp

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