Renesas H8S/2158, User Manual

Page: 817 / 929

Section 26 Clock Pulse Generator
Rev. 3.00 Jan 25, 2006 page 763 of 872
REJ09B0286-0300
Table 26.2 Crystal Resonator Parameters
Frequency(MHz) 5 8 10 12 16 20 25
R
S
(max) (
Ω
Ω Ω
Ω
) 100 80 70 60 50 40 30
C
0
(max) (pF) 7 7 7 7 7 7 7
26.1.2 External Clock Input Method
Figure 26.4 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 26.3. The frequency of the external clock should be the same as that of the system
clock (
φ
).
EXTAL
XTAL
External clock input
Open
(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 26.4 Example of External Clock Input