32186 datasheet(1023/1032 Pages) RENESAS

1023 / 1032 page

SUMMARY OF PRECAUTIONS

Appendix 4

Appendix 4-33

32185/32186 Group Hardware Manual

Rev.1.10 REJ09B0235-0110 May 15, 07

Appendix 4.16 Notes on Noise

(3) Wiring of the operation mode setup pins

When connecting the operation mode setup pins and the VCC or VSS pin, make sure they are wired in the

shortest distance possible.

The levels of the operation mode setup pins affect the microcomputer’s operation mode. When connecting

the operation mode setup pins and the VCC or VSS pin, be careful that no noise-induced potential differ-

ence will exist between the operation mode setup pins and the VCC or VSS pin. This is because the

presence of such a potential difference makes operation mode instable, which may result in the micro-

computer operating erratically or getting out of control.

VSS

Operation mode

setup pins

Noise

Long wiring

Short wiring

Operation mode

setup pins

(2) Wiring of clock input/output pins

Use as much thick and short wiring as possible for connections to the clock input/output pins.

When connecting a capacitor to the oscillator, make sure its grounding lead wire and the OSC-VSS pin on the

microcomputer are connected in the shortest distance possible (within 20 mm).

Also, make sure the VSS pattern used for clock oscillation is a large ground plane and is connected to GND.

The microcomputer operates synchronously with the clock generated by an oscillator circuit. Inclusion of

noise on the clock input/output pins causes the clock waveform to become distorted, which may result in

the microcomputer operating erratically or getting out of control. Furthermore, if a noise-induced potential

difference exists between the microcomputer’s VSS level and that of the oscillator, the clock fed into the

microcomputer may not be an exact clock.

Appendix Figure 4.16.2 Example Wiring of Clock Input/Output Pins

OSC-VSS

XIN

XOUT

VSS

Noise

Thick and short wiring

Thin and long wiring

OSC-VSS

XIN

XOUT

VSS

Appendix Figure 4.16.3 Example Wiring of the MOD0 and MOD1 Pins

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