Datasheet

Section 23 Clock Pulse Generator
Rev.7.00 Mar. 18, 2009 page 959 of 1136
REJ09B0109-0700
Table 23.2 Crystal Resonator 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
23.2.2 External Clock Input
An external clock signal can be input as shown in the examples in figure 23.4. 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 23.3 shows the input conditions for the external clock. When an external clock is used, the
range of its frequencies is from 8 to 25 MHz.
EXTAL
XTAL
External clock inpu
t
Open
(a) XTAL pin left open
EXTAL
XTAL
External clock inpu
t
(b) Counter clock input at XTAL pin
Figure 23.4 External Clock Input (Examples)