EM78P458AP datasheet(46/76 Pages) EMC

46 / 76 page

EM78P458/459

OTP ROM

below.

OSCI

OSCO

Ext.

Clock

EM78P458

EM78P459

Fig. 18 Circuit for External Clock Input

In the most applications, pin OSCI and pin OSCO can be connected with a crystal or ceramic

resonator to generate oscillation. Fig. 19 depicts such circuit. The same applies to the HXT mode and

the LXT mode. Table 12 provided the recommended values of C1 and C2. Since each resonator has

its own attribute, user should refer to their specifications for appropriate values of C1 and C2. RS, a

serial resistor, may be necessary for AT strip cut crystal or low frequency mode.

OSCI

OSCO

EM78P458

EM78P459

XTAL

Fig. 19 Circuit for Crystal/Resonator

Table 13 Capacitor Selection Guide for Crystal Oscillator or Ceramic Resonators

Oscillator Type

Frequency Mode

Frequency

C1(pF)

C2(pF)

455 kHz

100~150

2.0 MHz

20~40

Ceramic

Resonators

HXT

4.0 MHz

10~30

32.768kHz

100KHz

LXT

200KHz

455KHz

20~40

20~150

1.0MHz

15~30

2.0MHz

Crystal Oscillator

HXT

4.0MHz

3. External RC Oscillator Mode

For some applications that do not require precise timing calculation, the RC oscillator (Fig. 20) could

This specification is subject to change without prior notice.

06.25.2004 (V1.4)

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