7.5
Other signals
When designing an application, the EMC performance can be improved by closely studying:
•
Signals for which a temporary disturbance affects the running process permanently (the case of interrupts
and handshaking strobe signals, and not the case for LED commands). For these signals, a surrounding
ground trace, shorter lengths and the absence of noisy and sensitive traces nearby (crosstalk effect)
improve the EMC performance. For digital signals, the best possible electrical margin must be reached for
the two logical states and slow Schmitt triggers are recommended to eliminate parasitic states.
•
Noisy signals (such as clock).
•
Sensitive signals (such as high impedance).
7.6
Unused I/Os and features
All the microcontrollers are designed for a variety of applications and often a particular application does not use
100% of the MCU resources. To increase the EMC performance, unused clocks, counters or I/Os, should not be
left free, e.g. I/Os should be set to 0 or 1 (pull-up or pull-down to the unused I/O pins.) and unused features
should be frozen or disabled.
AN5419
Other signals
AN5419
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Rev 2
page 32/50