NRST trigger duration STM32H743XIH

[Yasmine-]

We are having trouble understanding the NRST pin characteristics.

The STM32H742xI/G STM32H743xI/G datasheet gives these parameters:

I have three questions:

1. What does 'input filtered' and 'input not filtered' pulse mean?

2. Is it by design true that a filtered reset trigger with a duration shorter than 50ns, will never be detected?

3. We use a 3.3V Vdd. Does a not-filtered pulse require 300ns or 1000ns duration to detect a reset?

[TDK · Accepted solution]

1. In this sense, "filtered" means the pulse is filtered out and doesn't produce a reset.

2. Yes. I would test it on your board and in your noise environment if you require this functionality. Noise on the pin can cause spurious resets, hence the recommendation for a decoupling cap close to the NRST pin.

3. Almost assuredly 300ns, despite the ambiguity in the datasheet. Lower voltage (i.e. 1.62 V to 1.71 V) will require a longer pulse.