32186 datasheet(1022/1032 Pages) RENESAS

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SUMMARY OF PRECAUTIONS

Appendix 4

Appendix 4-32

32185/32186 Group Hardware Manual

Rev.1.10 REJ09B0235-0110 May 15, 07

Appendix 4.16 Notes on Noise

The following describes precautions to be taken about noise and corrective measures against noise. The correc-

tive measures described here are theoretically effective for noise, but require that the application system incorpo-

rating those measures be fully evaluated before it can actually be put to use.

Appendix 4.16.1 Reduction of Wiring Length

Wiring on the board may serve as an antenna to draw noise into the microcomputer. Shorter the total wiring length,

the smaller the possibility of drawing noise into the microcomputer.

(1) Wiring of the RESET# pin

Reduce the length of wiring connecting to the RESET# pin. Especially when connecting a capacitor between

the RESET# and VSS pins, make sure it is wired to each pin in the shortest distance possible (within 20 mm).

Reset is a function to initialize the internal logic of the microcomputer. The width of a pulse applied to the

RESET# pin is important and is therefore specified as part of timing requirements. If a pulse in width

shorter than the specified duration (i.e., noise) is applied to the RESET# pin, the microcomputer will not be

reset for a sufficient duration of time and come out of reset before its internal logic is fully initialized,

causing the program to malfunction.

Appendix Figure 4.16.1 Example Wiring of the RESET# Pin

Reset

circuit

VSS

RESET#

VSS

RESET#

VSS

Noise

Reset

circuit

VSS

Long wiring

Short wiring

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