Datasheet

Table Of Contents
Section 21 Clock Pulse Generator
REJ09B0140-0900 Rev. 9.00 Page 671 of 846
Sep 16, 2010
H8S/2215 Group
21.2 System Clock Oscillator
The system clock can be supplied by connecting a crystal or ceramic resonator, or by input of an
external clock. Suitable resonators differ depending on the product. For details, see table 21.1.
Table 21.1 List of Suitable Resonators
Crystal Resonator Ceramic Resonator External Clock
H8S/2215 13 to 16 MHz 13 to 16 MHz
H8S/2215R 13 to 24 MHz 13 to 24 MHz
H8S/2215T 16, 24 MHz 16, 24 MHz
H8S/2215C 16 to 24 MHz 16 to 24 MHz
Legend:
: Not available
21.2.1 Connecting a Crystal Resonator
A crystal resonator can be connected as shown in the example in figure 21.2. Select the damping
resistance R
d
according to table 21.2. An AT-cut parallel-resonance crystal should be used.
EXTAL
XTAL
R
d
C
L2
C
L1
C
L1
=
C
L2
= 10 to 22 pF
(Recommended value, including
stray capacitance of circuit board)
Figure 21.2 Connection of Crystal Resonator (Example)
Table 21.2 Damping Resistance Value
Frequency (MHz) 13 16 24*
R
d
(Ω) 0 0 0
Note: * Available only in H8S/2215R and H8S/2215C.
Figure 21.3 shows the equivalent circuit of the crystal resonator. Use a crystal resonator that has
the characteristics shown in table 21.3.