CHAPTER 5 CLOCK GENERATOR
Preliminary User’s Manual U16846EJ1V0UD
93
(2) External RC oscillator
The external RC oscillator is oscillated by the resistor (R) and capacitor (C) connected across the CL1 and CL2
pins.
An external clock can also be input to the circuit. In this case, input the clock signal to the CL1 pin, and input the
inverted signal to the CL2 pin.
Figure 5-11 shows the external circuit of the external RC oscillator.
Figure 5-11. External Circuit of External RC Oscillator
(a) RC oscillation
(b) External clock
V
SS
CL1
CL2
R
C
External
clock
CL1
CL2
Caution When using the external RC oscillator, wire as follows in the area enclosed by the broken lines
in Figure 5-11 to avoid an adverse effect from wiring capacitance.
•
Keep the wiring length as short as possible.
•
Do not cross the wiring with the other signal lines. Do not route the wiring near a signal line
through which a high fluctuating current flows.
•
Always make the ground point of the oscillator capacitor the same potential as V
SS
. Do not
ground the capacitor to a ground pattern through which a high current flows.
•
Do not fetch signals from the oscillator.
Figure 5-12 shows an example of incorrect resonator connections.
