7733 datasheet(609/940 Pages) RENESAS

609 / 940 page

7733 Group User’s Manual

21-61

APPENDIX

Appendix 8. Countermeasure examples against noise

General countermeasure examples against noise are described below. Although the effect of these

countermeasures depends on each system, refer to the following when a noise-related problem occurs.

1. Shortest wiring length

The wiring on a printed circuit board may function as an antenna which feeds noise into the microcomputer.

The shorter the total wiring length (by mm unit), the less possibility of noise insertion into the microcomputer.

______

(1) Wiring for pin RESET

______

Make the length of wiring connected to pin RESET as short as possible. In particular, connect a

______

capacitor between pin RESET and pin Vss with the shortest possible wiring (within 20 mm).

Reason

______

If noise is input to pin RESET, the microcomputer

restarts operation before the internal state of

the microcomputer is completely initialized. This

may cause a program runaway.

______

Fig. 12 Wiring for pin RESET

RESET

Reset

circuit

Noise

Vss

M37733MHBXXXFP

Not acceptable

Reset

circuit

RESET

VSS

M37733MHBXXXFP

Acceptable

Appendix 8. Countermeasure examples against noise

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