
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.
<Reasons>
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.
<Reasons>
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