Datasheet

Section 23 Clock Pulse Generator
Rev. 6.00 Mar. 18, 2010 Page 771 of 982
REJ09B0054-0600
Table 23.1 Damping Resistance Value
Frequency (MHz) 2
*
1
4
*
1
6
*
1
8
*
1
10 12 16
*
2
20
*
2
R
d
(Ω) 1 k 500 300 200 100 0 0 0
Notes: 1. The H8S/2258 Group is out of operation.
2. Supported only by the H8S/2239 Group.
Figure 23.3 shows the equivalent circuit of the crystal resonator. Use a crystal resonator that has
the characteristics shown in table 23.2.
XTAL
C
L
AT-cut parallel-resonance type
EXTAL
C
0
LR
s
Figure 23.3 Crystal Resonator Equivalent Circuit
Table 23.2 Crystal Resonator Characteristics
Frequency (MHz) 2
*
1
4
*
1
6
*
1
8
*
1
10 12 16
*
2
20
*
2
R
S
max (Ω) 500 120 100 80 60 60 50 40
C
0
max (pF) 7 7 7 7 7 7 7 7
Notes: 1. The H8S/2258 Group is out of operation.
2. Supported only by the H8S/2239 Group.
23.2.2 External Clock Input
An external clock signal can be input as shown in the examples in figure 23.4. If the XTAL pin is
left open, ensure that stray capacitance does not exceed 10 pF. When complementary clock is
input to the XTAL pin, the external clock input should be fixed high in standby mode, subactive
mode, subsleep mode, or watch mode.