M16C62_M Datasheet, PDF (609/615 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/60 SERIES

Appendix 5
Mitsubishi microcomputers
M16C / 62A Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
1.4 Oscillator concerns
Take care to prevent an oscillator that generates clocks for a microcomputer operation from being affected
by other signals.
1.4.1 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
VSS
XOUT
GND
Figure 1.4.1. Wiring for a large current signal line
1.4.2 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. Or do not stretch long such signal lines parallelly to these said lines.
q Reason
Signal lines where potential levels change frequently (such as the TAOUT 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.
Do not cross
TAOUT
XIN
VSS
XOUT
N.G.
Figure 1.4.2. Wiring of signal lines where potential levels change frequently
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