S32K RESET_B pin filter

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S32K RESET_B pin filter

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Contributor II

Hello,

I have a question about RESET_B pin filter.

I found the description about RESET_B pin in 23.2.2.1.1 "RESET_B pin filter" on S32K RM Rev.3

while I found another description about RESET_B pin in Table 8. on S32K DS Rev.3

as WFRST parameter(threshold around 100ns).

Are the implementations of these functions same or different?

I guess these are different implementation and they are implemented as cascade.

Best Regards,

Ikki

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6 Replies

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NXP TechSupport
NXP TechSupport

Hello,

Your understanding seems to be correct.

As per the datasheet, even though the filter is not used, the minimum pulse length must be 100ns to be recognized. To filter pulses with length greater than 100ns the digital filter is needed.

Regarding LPO128K, it has fixed filter value, pulse with length up to 2 cycles (15.6 us) will always get filtered. Using bus clock, the value must be set in RCM_RPC[RSTFLTSEL].

Regards,

Daniel

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Contributor II

Hello, Daniel

OK, I have already understood your information from RM & DS descriptions.

However I cannot have the confidence from only the description because that is just literal information.

What I want is the implementation, in other words, whether both filters are implemented as different functions.

Could you confirm your designer about this?

Best Regards,

Ikki

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102 Views
NXP TechSupport
NXP TechSupport

Hello Ikki,

Sorry for my late response.

Based on the answer I’ve received the Reset control module requires 100ns pulse.

Both filters (passive, digital) are features of the Port module and can be disabled. Therefore, it is in a cascade.

Nevertheless, the description is still confusing and I’m expecting to receive more details.

Regards,

Daniel

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102 Views
Contributor II

Hello Daniel,

Thank you for your responce.

I understand the two RESET_B filters are in a cascade.

However, there would be some points which are different as what I understand.
From your comment:
> Both filters (passive, digital) are features of the Port module and can be disabled.
Do you mean "passive" filter is described as WFRST parameter(threshold around 100ns)?
Then,
 - I understand the passive filter is implemented not on Port module but another system function.
 - I understand there is no implementation of disabling function for the passive filter independently.
Is my understanding not properly?

Regards,

Ikki

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102 Views
NXP TechSupport
NXP TechSupport

Hello,

The passive filter is a feature of the Port module, as you can see in the chapter 10.3.1. As per excel sheet S32K144_IO_Signal_Description… (peripheral summaries) attached to the RM. The reset pin is one of pins where the filter is available, enabled after reset and configurable (PORT_PCRn[PFE]), so actually it can be disabled. In fact, I have received confirmation that both filters can be disabled, but even without the filter it takes time for the reset to be recognized.    

However, according to Table 23-2 (FTFC_FOPT definition), when the RESET_PIN_CONFIG is set, the passive filter is also enabled.

If my understanding is correct, the WFRTS (100ns) is a threshold of the passive filter provided the passive filter is enabled. I have asked for confirmation, but I’m still waiting.

 

Regards,

Daniel

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NXP TechSupport
NXP TechSupport

Hello,

I’m still waiting for an answer from designers.

 

Regards,

Daniel

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