Other Signals; Unused I/Os And Features - ST STM32F0 Series Application Note

Recommendations
Figure 12. Typical layout for V
6.5

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
(such as interrupts and handshaking strobe signals, but not LED commands). For
these signals, a surrounding ground trace, shorter lengths and the absence of noisy
and sensitive traces nearby (crosstalk effect) improve EMC performance.
●
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 (clock, etc.)
●
Sensitive signals (high impedance, etc.)
6.6

Unused I/Os and features

All microcontrollers are designed for a variety of applications and often a particular
application does not use 100% of the MCU resources.
To increase EMC performance and avoid extra power consumption, unused clocks, counters
or I/Os, should not be left free. I/Os should be connected to a fixed logic level of 0 or 1 by an
external or internal pull-up or pull-down on the unused I/O pin. The other option is to
configure GPIO as output mode using software. Unused features should be frozen or
disabled, which is their default value.
22/29
/V pair
DD SS
Via to V
DD
Cap.
V V
DD
STM32F0xxx
Doc ID 023035 Rev 2
Via to V
SS
SS
AN4080