4502 datasheet(59/214 Pages) RENESAS

59 / 214 page

1-47

4502 Group

HARDWARE

Rev.2.01

Feb 02, 2005

REJ09B0193-0201

Fig. 43 Switch to ceramic resonance/RC oscillation

Fig. 44 Handling of XIN and XOUT when operating on-chip oscillator

Fig. 45 Ceramic resonator external circuit

Fig. 46 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) Selection of source oscillation (f(XIN))

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

oscillation of the 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

can be selected only at once. The oscillation circuit corresponding

to the first executed one of these two instructions is valid. Other os-

cillation circuit 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, the MCU operates by the on-chip oscilla-

tor.

(2) On-chip oscillator operation

When the MCU operates by the on-chip oscillator as the source os-

cillation (f(XIN)) without using the ceramic resonator or the RC

oscillator, connect XIN pin to VSS and leave XOUT pin open (Figure

44).

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

voltage and the operation temperature range.

Be careful that variable frequencies when designing application

products.

(3) Ceramic resonator

When the ceramic resonator is used as the source oscillation

(f(XIN)), connect 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 45).

(4) RC oscillation

When the RC oscillation is used as the source oscillation (f(XIN)),

connect the XIN pin to the external circuit of resistor R and the ca-

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

execute the CRCK instruction (Figure 46).

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

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

limits.

4502

XIN

XOUT

Execute the CRCK

instruction in program.

4502

XIN

XOUT

CIN

COUT

4502

XIN

XOUT

Do not use the CMCK instruction

and CRCK instruction in program.

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

FUNCTION BLOCK OPERATIONS

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