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5. Setup for I/O ports
Setup I/O ports by hardware and software as follows:
<Hardware protection>
Connect a resistor of 100 ohms or more to an I/O port in series.
<Software protection>
As for an input port, read data several times for checking whether input levels are equal or not.
As for an output port, since the output data may reverse because of noise, rewrite data to its port Pi
register periodically.
Rewrite data to port Pi direction registers periodically.
Fig. 15. Setup for I/O ports
Appendix 8. Examples of noise immunity improvement
Data bus
Direction register
Port latch
7751 Group User's Manual
APPENDIX
Noise
Port
20–69
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