HD64F2145 Datasheet, PDF (650/829 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

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 of 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 the equivalent circuit of a crystal resonator. A resonator having the
characteristics given in table 25.2 should be used.
A crystal resonator with frequency identical to that of the system clock (ø) should be used.
C_L1
EXTAL
XTAL
R_d
C_L2
C_L1 = C_L2 = 10 to 22 pF
Figure 25.2 Typical Connection to Crystal Resonator
Table 25.1 Damping Resistance Values
Frequency (MHz)
2
4
8
10
12
16
20
R_d (Ω)
1k
500
200
0
0
0
0
XTAL
C_L
L
R_s
EXTAL
C₀
AT-cut parallel-resonance crystal resonator
Figure 25.3 Equivalent Circuit of Crystal Resonator
Rev. 2.0, 08/02, page 610 of 788