Datasheet

Section 23 Clock Pulse Generator
Rev.7.00 Mar. 18, 2009 page 958 of 1136
REJ09B0109-0700
23.2 Oscillator
Clock pulses can be supplied by connecting a crystal resonator, or by input of an external clock.
23.2.1 Connecting a Crystal Resonator
A crystal resonator can be connected as shown in the example in figure 23.2. Select the damping
resistance R
d
according to table 23.1. An AT-cut parallel-resonance type should be used.
Figure 23.3 shows the equivalent circuit of the crystal resonator. Use a crystal resonator that has
the characteristics shown in table 23.2. When a crystal resonator is used, the range of its
frequencies is from 8 to 25 MHz.
EXTAL
XTAL
Note: * CL1 = CL2 = 10 pF on the H8S/2378 0.18µm F-ZTAT Group and
H8S/2378R 0.18µm F-ZTAT Group
R
d
C
L2
C
L1
C
L1
= C
L2
= 10 to 22 pF*
Figure 23.2 Connection of Crystal Resonator (Example)
Table 23.1 Damping Resistance Value
Frequency (MHz) 8 12 16 20 25
R
d
(Ω) 200 0 0 0 0
XTAL
C
L
AT-cut parallel-resonance type
EXTAL
C
0
LR
s
Figure 23.3 Crystal Resonator Equivalent Circuit