Datasheet
Section 22 Clock Pulse Generator
Rev.6.00 Mar. 18, 2009 Page 816 of 980
REJ09B0050-0600
22.2 Oscillator
Clock pulses can be supplied by connecting a crystal resonator, or by input of an external clock.
22.2.1 Connecting a Crystal Oscillator
A crystal oscillator can be connected as shown in the example in figure 22.2. Select the damping
resistance R
d
according to table 22.1. An AT-cut parallel-resonance type should be used.
When a clock is supplied with a crystal resonator connected, the frequency of the crystal resonator
should be 8 MHz to 25 MHz.
Figure 22.3 shows the equivalent circuit of the crystal oscillator. Use a crystal oscillator that has
the characteristics shown in table 22.2.
EXTAL
XTAL
Note: * In the H8S/2368 0.18 μm F-ZTAT Group, C
L1
= C
L2
= 10 pF.
R
d
C
L2
C
L1
C
L1
= C
L2
= 10 to 22 pF
*
Figure 22.2 Connection of Crystal Oscillator (Example)
Table 22.1 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 22.3 Crystal Oscillator Equivalent Circuit