External Clock Input Method - Renesas H8S/2100 Series Hardware Manual

Table 25.2 Crystal Resonator Parameters
Frequency (MHz)
R (max) (Ω)
S
C (max) (pF)
0
25.1.2

External Clock Input Method

Figure 25.4 shows a typical method of inputting 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 or 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 (φ).
EXTAL
XTAL
EXTAL
XTAL
8
80
7
(a) Example of external clock input when XTAL pin is left open
(b) Example of external clock input when an inverted clock is input to XTAL pin
Figure 25.4 Example of External Clock Input
10 12
70 60
7 7
External clock input
Open
External clock input
Rev. 1.00 Apr. 28, 2008 Page 835 of 994
Section 25 Clock Pulse Generator
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