H8SSLASH2218 datasheet(648/750 Pages) RENESAS

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Section 19 Clock Pulse Generator

Rev.6.00 Jun. 03, 2008 Page 600 of 698

REJ09B0074-0600

19.2

System Clock Oscillator

Clock pulses can be supplied by connecting a crystal resonator, or by input of an external clock.

19.2.1

Connecting a Crystal Resonator

A crystal resonator can be connected as shown in the example in figure 19.2. Select the damping

resistance Rd according to table 19.1. An AT-cut parallel-resonance crystal should be used.

EXTAL

XTAL

= CL2 = 10 to 22 pF

(Recommended value, including

stray capacitance of circuit board)

Figure 19.2 Connection of Crystal Resonator (Example)

Table 19.1

Damping Resistance Value

Frequency (MHz)

Rd (Ω)

300

200

100

Figure 19.3 shows the equivalent circuit of the crystal resonator. Use a crystal resonator that has

the characteristics shown in table 19.2.

XTAL

AT-cut parallel-resonance type

EXTAL

Figure 19.3 Crystal Resonator Equivalent Circuit

Table 19.2

Crystal Resonator Characteristics

Frequency (MHz)

RS max (Ω)

100

C0 max (pF)

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