GPIO Filter (enabled with PFE)

[yvesb]

Hello,

in the ref manual of the K20 series, I found the following sentence very confusing:

A low pass filter of 10 MHz to 30 MHz bandwidth.

could someone please tell me what is the exact nature of the input filter activated with PORTx_PCRn register bit PFE?

(band pass of 10MHz to 30MHz bandwidth or low pass with 10MHz to 30MHz cutoff frequency)

regards,

Yves

[adriancano · Accepted solution]

Hi,

The PFE field in the PORTx_PCRn register enables a low pass filter; this low pass filter's frequency is affected by the environment temperature. This is: if the temperature increases the low pass filter bandwidth will become narrow, this means that the signal frequencies more than 30 MHz will be filtered at low temperature and in some devices at high temperatures the 10 MHz signals will be filtered.

This is the reason why in the PFE field the low pass filter is explained as a low pass filter of 10 MHz to 30 MHz bandwidth.

I hope this information can help you.

Regards,

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