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What is ''Reset temporization''

Uwe Bonnes
Principal III

‎2018-03-27 3:44 AM

Posted on March 27, 2018 at 12:44

Hello,

STM32 parts define a Reset temporization time (T RSTTEMPO) several 100 us long up to 4.5 ms on STM32F103. I did not find an explanation for this time, but I suspect this is the time from the nRST Pin reaching a valid high level to chip internal reset deasserted. Is this guess right?

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Max
ST Employee

‎2018-03-27 6:02 AM

Posted on March 27, 2018 at 15:02

Hello

Bonnes.Uwe

,

This temporization is notimpacting the signal coming from the NRST pin.

It is linked to the POR (Power On Reset), which has a somewhat strongereffect thana regular system reset.

For example, it forces option byte loading and some registers are only reset bya POR (like debug registers)

The POR only happens when powering up and exiting from standby. Other reset sources are not delayed.

The temporization starts when V

DD

crosses theV

POR/PDR

threshold.

The only explanation lays in fig.5 page 69 of the

http://www.st.com/content/ccc/resource/technical/document/reference_manual/59/b9/ba/7f/11/af/43/d5/CD00171pdf/files/CD00171pdf/jcr:content/translations/en.CD00171pdf

(rev18)

This

temporization may be visible on the NRST pin (if the pin is not driven low externally) because it is forced low internallyduring the tempo.

But keep in mind there is a filter on NRST pin to reducenoise sensitivity (seeNRST pin characteristics tablein the datasheet)

0690X0000060AGmQAM.png

This means pulse shorter than 100ns are always filtered out so no reset

This means pulselargerthan 300ns arenever filtered outandtherefore always generate a reset.

In between: it's pure luck...

Best regards,

Max

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Max
ST Employee

‎2018-03-27 7:04 AM

Posted on March 27, 2018 at 16:04

It's actually just a delay.

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Andrew Neil
Guru
In response to Max

‎2018-03-27 8:23 AM

Posted on March 27, 2018 at 15:23

So what does '

temporization' actually mean??

It is a made-up word - so please supply the corresponding definition!

EDIT

or perhaps it is a mis-translation of something?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.
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waclawek.jan
Guru
In response to Andrew Neil

‎2018-03-27 9:06 AM

Posted on March 27, 2018 at 16:06

https://en.wiktionary.org/wiki/temporization

 

https://en.wiktionary.org/wiki/temporisation ♯ French

 

2. (technics)

https://en.wiktionary.org/wiki/timer

(launching an action after a given

https://en.wiktionary.org/wiki/delay

)

?

ST is a French-Italian company.

JW

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Andrew Neil
Guru
In response to Max

‎2018-03-27 11:23 AM

Posted on March 27, 2018 at 18:23

Then please can the document be revised to say that!

As you can see, the current wording is incomprehensible!

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.
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waclawek.jan
Guru
In response to Andrew Neil

‎2018-03-27 4:05 PM

Posted on March 27, 2018 at 23:05

I wish this be the most incomprehensible wording in the STM32 documents.

Jan

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