System Clock Oscillator; X1 Oscillator - NEC mPD78F0730 Preliminary User's Manual

5.4 System Clock Oscillator

5.4.1 X1 oscillator

The X1 oscillator oscillates with a crystal resonator or ceramic resonator (1 to 20 MHz) connected to the X1 and X2
pins.
Figure 5-11 shows an example of the external circuit of the X1 oscillator.
Figure 5-11. Example of External Circuit of X1 Oscillator (Crystal or Ceramic Oscillation)
Cautions 1. When using the X1 oscillator, wire as follows in the area enclosed by the broken lines in the
Figure 5-12 shows examples of incorrect resonator connection.
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CHAPTER 5 CLOCK GENERATOR
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
not ground the capacitor to a ground pattern through which a high current flows.
• Do not fetch signals from the oscillator.
Figure 5-12. Examples of Incorrect Resonator Connection (1/2)
(a) Too long wiring
V X1 X2
SS
Preliminary User's Manual U19014EJ1V0UD
V
SS
X1
X2
Crystal resonator
or
ceramic resonator
(b) Crossed signal line
V
SS
SS
PORT
X1 X2
. Do