18.2
Oscillator
Clock pulses can be supplied by connecting a crystal resonator, or by input of an external clock.
18.2.1
Connecting Crystal Resonator
A crystal resonator can be connected as shown in the example in figure 18.2. Select the damping
resistance R
d
When the clock is provided by connecting a crystal resonator, a crystal resonator having a
frequency of 4 to 9 MHz should be connected.
Table 18.1 Damping Resistance Value
Frequency (MHz)
R
(Ω)
d
Figure 18.3 shows an equivalent circuit of the crystal resonator. Use a crystal resonator that has
the characteristics shown in table 18.2.
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according to table 18.1. An AT-cut parallel-resonance type should be used.
EXTAL
XTAL
R
d
Figure 18.2 Connection of Crystal Resonator (Example)
4
500
XTAL
Figure 18.3 Crystal Resonator Equivalent Circuit
C
L1
10 pF ≤ C
C
L2
6
300
C
L
L
R
s
AT-cut parallel-resonance type
C
0
Section 18 Clock Pulse Generator
≤ 22 pF
= C
L1
L2
8
9
200
100
EXTAL
Rev. 3.00 Mar. 14, 2006 Page 665 of 804
REJ09B0104-0300