M16CSLASH62 datasheet(609/615 Pages) RENESAS

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Appendix 5

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

2-292

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.

XIN

XOUT

VSS

Microcomputer

Mutual inductance

Large

current

GND

XIN

XOUT

VSS

TAOUT

Do not cross

N.G.

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.

Figure 1.4.2. Wiring of signal lines where potential levels change frequently

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