88
4.2
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.
1. Connecting a crystal oscillator
Figure 4.2 shows a typical method of connecting a crystal oscillator.
1
2
C
1
C
2
OSC
OSC
R = 1 M
±
20%
f
Ω
R
f
Oscillation
frequency
4.0 MHz
Manufacturer
Nihon Denpa Kogyo
C
1
, C
2
Recommendation
value
12 pF
±
20%
Products Name
NR-18 (NDK03)
Figure 4.2 Typical Connection to Crystal Oscillator
Figure 4.3 shows the equivalent circuit of a crystal oscillator. An oscillator having the
characteristics given in table 4.1 should be used.
C
S
C
0
R
S
OSC
1
OSC
2
L
S
Figure 4.3 Equivalent Circuit of Crystal Oscillator
Table 4.1
Crystal Oscillator Parameters
Frequency (MHz)
4.193
RS max (
Ω
)
100
C
0
(pF)
16 pF