UPD784938 Datasheet, PDF (112/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 4 CLOCK GENERATOR
4.4.2 When crystal/ceramic oscillation is used
(1) As the oscillator is a high-frequency analog circuit, considerable care is required.
The following points, in particular, require attention.
• 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 VSS. Do not ground the capacitor
to a ground pattern through which a high current flows.
• Do not fetch signals from the oscillator.
If oscillation is not performed normally and stably, the microcontroller will not be able to operate normally and
stably, either. Also, if a high-precision oscillation frequency is required, consultation with the oscillator manufacturer
is recommended.
Figure 4-6. Cautions on Resonator Connection
µPD784938
X2
X1
VSS
Cautions 1. The oscillator should be as close as possible to the X1 and X2 pins.
2. No other signal lines should pass through the area enclosed by the broken lines.
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Preliminary User’s Manual U13987EJ1V0UM00