External Clock Input - Renesas F-ZTAT H8 Series Hardware Manual

Avoid
C
L2
C
L1
20.2.2

External Clock Input

Circuit Configuration: An external clock signal can be input as shown in the examples in figure
20.5. The external clock is input from the EXTAL pin. If the XTAL pin is left open, the stray
capacitance should not exceed 10 pF. If the stray capacitance at the XTAL pin exceeds 10 pF in
configuration a, use configuration b instead and hold the clock high in standby mode.
Signal A
Figure 20.4 Example of Incorrect Board Design
EXTAL
XTAL
a. XTAL pin left open
EXTAL
74HC04
XTAL
b. Complementary clock input at XTAL pin
Figure 20.5 External Clock Input (Examples)
Section 20 Clock Pulse Generator
Signal B
XTAL
EXTAL
External clock input
Open
External clock input
Rev. 7.00 Sep 21, 2005 page 657 of 878
H8/3048 Group
REJ09B0259-0700