Renesas H8S/2100 Series, Hardware Manual

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Section 25 Clock Pulse Generator
Rev. 1.00 Apr. 28, 2008 Page 834 of 994
REJ09B0452-0100
25.1 Oscillator
Clock pulses can be supplied either by connecting a crystal resonator or by providing external
clock input.
25.1.1 Connecting Crystal Resonator
Figure 25.2 shows a typical method for connecting a crystal resonator. An appropriate damping
resistance R
d
, given in table 25.1 should be used. An AT-cut parallel-resonance crystal resonator
should be used.
Figure 25.3 shows an equivalent circuit of a crystal resonator. A crystal resonator having the
characteristics given in table 25.2 should be used.
The frequency of the crystal resonator should be the same as that of the system clock (
φ
).
EXTAL
XTAL
R
d
C
L2
C
L1
C
L1
= C
L2
= 10 to 22 pF
Figure 25.2 Typical Connection to Crystal Resonator
Table 25.1 Damping Resistor Values
Frequency (MHz) 8 10 12 16 20
R
d
(
Ω
) 200 0 0 0 0
XTAL
C
L
AT-cut parallel-resonance crystal resonator
EXTAL
C
0
L R
s
Figure 25.3 Equivalent Circuit of Crystal Resonator