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5.2
System Clock Generator
Clock pulses can be supplied to the system clock divider either by connecting a crystal or ceramic
oscillator, or by providing external clock input.
Connecting a Crystal Oscillator: Figure 5.2 shows a typical method of connecting a crystal
oscillator. An AT-cut parallel-resonance crystal resonator should be used.
Figure 5.3 shows the equivalent circuit of a crystal oscillator. An oscillator having the
characteristics given in table 5.1 should be used.
OSC
1
Table 5.1
Crystal Oscillator Parameters
Frequency
R
(max)
S
C
(max)
0
76
OSC
1
OSC
2
Figure 5.2 Typical Connection to Crystal Oscillator
L
S
Figure 5.3 Equivalent Circuit of Crystal Oscillator
2 MHz
4 MHz
500 Ω
120 Ω
7 pF
7 pF
C
1
C = C = 12 pF ±20%
1
C
2
C
S
C
0
8 MHz
80 Ω
7 pF
2
R
S
10 MHz
60 Ω
7 pF
OSC
2
16 MHz
50 Ω
7 pF
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