M38509M2-XXXSS View Datasheet(PDF) - Renesas Electronics
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M38509M2-XXXSS Datasheet PDF : 287 Pages
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APPENDIX
3.4 Countermeasures against noise
3.4.4 Oscillator concerns
Take care to prevent an oscillator that generates clocks for a microcomputer operation from being affected
by other signals.
(1) Keeping oscillator away from large current signal lines
Install a microcomputer (and especially an oscillator) as far as possible from signal lines where a
current larger than the tolerance of current value flows.
q Reason
In the system using a microcomputer, there are signal lines for controlling motors, LEDs, and
thermal heads or others. When a large current flows through those signal lines, strong noise
occurs because of mutual inductance.
Mutual inductance
M
Microcomputer
Large
current
XIN
XOUT
VSS
GND
Fig. 3.4.8 Wiring for a large current signal line
(2) Installing oscillator away from signal lines where potential levels change frequently
Install an oscillator and a connecting pattern of an oscillator away from signal lines where potential
levels change frequently. Also, do not cross such signal lines over the clock lines or the signal lines
which are sensitive to noise.
q Reason
Signal lines where potential levels change frequently (such as the CNTR pin signal line) may affect
other lines at signal rising edge or falling edge. If such lines cross over a clock line, clock waveforms
may be deformed, which causes a microcomputer failure or a program runaway.
N.G.
Do not cross
CNTR
XIN
XOUT
VSS
Fig. 3.4.9 Wiring of RESET pin
3850 Group (Spec. H) User’s Manual
3-47
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