Datasheet

Section 22 Clock Pulse Generator
Rev.6.00 Mar. 18, 2009 Page 817 of 980
REJ09B0050-0600
Table 22.2 Crystal Oscillator Characteristics
Frequency (MHz) 8 12 16 20 25
R
S
max (Ω) 80 60 50 40 40
C
0
max (pF) 7 7 7 7 7
22.2.2 External Clock Input
An external clock signal can be input as shown in the examples in figure 22.4. If the XTAL pin is
left open, make sure that parasitic capacitance is no more than 10 pF. When the counter clock is
input to the XTAL pin, make sure that the external clock is held high in standby mode.
Table 22.3 shows the input conditions for the external clock. The frequency of an external clock to
be input should be 8 MHz to 25 MHz.
EXTAL
XTAL
External clock input
Open
(a) XTAL pin left open
EXTAL
XTAL
External clock input
(b) Counter clock input at XTAL pin
Figure 22.4 External Clock Input (Examples)