HD64F3028F25 Datasheet, PDF (658/925 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series

19.2 Oscillator Circuit
Clock pulses can be supplied by connecting a crystal resonator, or by input of an external clock
signal.
19.2.1 Connecting a Crystal Resonator
Circuit Configuration: A crystal resonator can be connected as in the example in figure 19.2.
Damping resistance Rd should be selected according to table 19.1 (1), and external capacitances
C_L1 and C_L2 according to table 19.1 (2). An AT-cut parallel-resonance crystal should be used.
C_L1
EXTAL
XTAL
Rd
C_L2
Figure 19.2 Connection of Crystal Resonator (Example)
If a crystal resonator with a frequency higher than 16 MHz is connected, the external load
capacitance values in table 19.1 (2) should not exceed 10 [pF]. Also, in order to improve the
accuracy of the oscillation frequency, a thorough study of oscillation matching evaluation, etc.,
should be carried out when deciding the circuit constants.
Table 19.1 (1) Damping Resistance Value
Damping
Frequency f (MHz)
Resistance
Value
2 2 < f ≤ 4 4 < f ≤ 8 8 < f ≤ 10 10 < f ≤ 13 13 < f ≤ 16 16 < f ≤ 18 18 < f ≤ 25
Rd (Ω) 1 k 500
200
0
0
0
0
0
Note: A crystal resonator between 2 MHz and 25 MHz can be used. If the chip is to be operated
at less than 2 MHz, the on-chip frequency divider should be used. (A crystal resonator of
less than 2 MHz cannot be used.)
Table 19.1 (2) External Capacitance Values
External Capacitance Value
Frequency f (MHz)
CL1 = CL2 (pF)
2 ≤ f ≤ 16
22
3.3 V Version
16 < f ≤ 25
10
Rev. 2.00, 09/03, page 626 of 890