HD64F2145 Datasheet, PDF (651/829 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

Table 25.2 Crystal Resonator Parameters
Frequency (MHz)
2
4
8
10
12
16
20
R_S (max) (Ω)
C (max) (pF)
0
500
120
80
70
60
50
40
7
25.1.2 External Clock Input Method
Figure 25.4 shows a typical method of connecting an external clock signal. To leave the XTAL pin
open, incidental capacitance should be 10 pF or less.
To input an inverted clock to the XTAL pin, the external clock should be set to high in standby
mode, subactive mode, subsleep mode, and watch mode. External clock input conditions are
shown in table 25.3. The frequency of the external clock should be the same as that of the system
clock (ø).
EXTAL
XTAL
Open
External clock input
(a) Example of external clock input when XTAL pin left open
EXTAL
XTAL
External clock input
(b) Example of external clock input when an inverted clock is input to XTAL pin
Figure 25.4 Example of External Clock Input
Rev. 2.0, 08/02, page 611 of 788