Datasheet

Section 24 Clock Pulse Generator
Rev. 3.00 Mar 21, 2006 page 635 of 788
REJ09B0300-0300
Table 24.2 Crystal Resonator Parameters
Frequency (MHz) 2 4 8 10 12 16 20
R
S
(max) (Ω) 500 120 80 70 60 50 40
C
0
(max) (pF) 7 7 7 7 7 7 7
24.1.2 External Clock Input Method
Figure 24.4 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 24.3. 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 24.4 Example of External Clock Input