System Clock Oscillators; System Clock Oscillator; External Circuit Of System Clock Oscillator - NEC switch User Manual

5.4 System Clock Oscillators

5.4.1 System clock oscillator

The system clock oscillator is oscillated by the crystal resonator (6.0 MHz TYP.) connected across the X1 and X2
pins.
An external clock can also be input to the circuit. In this case, input the clock signal to the X1 pin, and leave the
X2 pin open.
Figure 5-3 shows the external circuit of the system clock oscillator.
(a) Crystal oscillation
Crystal resonator
Caution When using the system clock oscillator, wire as follows in the area enclosed by the broken
lines in Figure 5-3 to avoid an adverse effect from wiring capacitance.
• • • • Keep the wiring length as short as possible.
• • • • Do not cross the wiring with 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
ground the capacitor to a ground pattern through which a high current flows.
• • • • Do not fetch signals from the oscillator.
CHAPTER 5 CLOCK GENERATOR
Figure 5-3. External Circuit of System Clock Oscillator
V
SS0
X1
X2
User's Manual U12978EJ3V0UD
(b) External clock
External
X1
clock
OPEN
X2
. Do not
SS0
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