B3-18

EM78P156E

Table 7 The summary of maximum operating speeds

Conditions

VDD (V)

Fxt max. (MHz)

2.5

8

Two clocks

3

12

518

6.4

20

2.5

16

Four clocks

3

24

536

6.5

40

2. Crystal Oscillator/Ceramic Resonators (XTAL)

EM78P156E can be driven by an external clock signal through the OSCI pin as shown in Fig.11

Ext. Clock

OSCI

OSCO

EM78P156E

Fig. 11 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.12 depicts the circuit. It is the same no matter in the HXT mode or in the LXT mode. Table 8

recommends the values of C1 and C2. Since each resonator has its own attribute, users 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

EM78P156E

C1

C2

XTAL

RS

Fig. 12 Circuit for Crystal/Resonator