ST25R3911B NRE IRQ firing - Errata document

gentilkiwi · ‎2025-08-06

Hello,

I'm experiencing somme issues on the ST25R3911B with the TIM/NRE IRQ firing, even after the end of receive (but without the nrt_emv flag).

> Basically the nrt_on flag is on even after receive, and I'm forced to send a CLEAR_FIFO/ STOP to stop this timer instead of having it stopped automatically.

I saw some errata references in the RFAL source code, but I don't find the errata documentation on the component webpage. Maybe I missed something, or can you please help me to find it? - https://www.st.com/en/nfc/st25r3911b.html#documentation

Bonus part: if you have the documentation and errata for ST25R3911 (not B) too, I will be interested.

Thank you in advance for your help :)

Brian TIDAL · ‎2025-08-06

Hi,

For the Errata Sheet, I cannot do more than recommend you to contact your local ST sales and marketing department to obtain this document.

Regarding the ST25R3911, as explained in the PTN: "The part will not be transferred." Therefore, this device is not part of the ST portfolio.

All silicon workarounds available in the ST25R3911B RFAL code apply to the ST25R3911B.

Rgds

BT

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Brian TIDAL · ‎2025-08-06

Hi,

This document related to ST25R3911B is not publicly available. Contact your local ST sales and marketing department to obtain this document.

As far as I know, the ST25R3911 (not B) is not part of the ST portfolio. Do you mean ST25R3912 or ST25R3914?

Rgds

BT

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gentilkiwi · ‎2025-08-06

Hi Brian,

Thank you for quick answer.

I'm a little bit lost: both ST25R3916 and ST25R3916B have public erratas, but not ST25R3911B ? What are terrible secrets inside ?

As I'm an individual I don't have a local ST sales and marketing department, and I don't understand the idea to hide to others developpers this kind of information?

No, I mean ST25R3911 - The RFAL source code hase some errata references for 3911, and others for 3911B - it was on ST portfolio: https://web.archive.org/web/20180427204240/http://www.st.com/en/nfc/st25r3911.html

Brian TIDAL · ‎2025-08-06

Hi,

As most customers build their applications on top of the RFAL, the Errata Sheet for the ST25R3911B is not publicly available. Using the RFAL is highly recommended. All silicon workarounds are openly documented in the publicly available RFAL code and apply to the ST25R3911B.

The official names for the ST25R3911B and its variants are: ST25R3911B, ST25R3912, ST25R3914, and ST25R3915. The name ST25R3911 may have been used at an early stage, but it is not part of the ST portfolio.

Rgds

BT

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gentilkiwi · ‎2025-08-06

Hi Brian,

Thank you for your answer.

I don't see the point making the ST25R3911B errata not public? Having the best documentation helps all developpers.

I love the RFAL for a lot of use cases - especially high level protocols, but I find the low level chip communication part inneficient and prefer to code mine.

From source I find for the ST25R3911:

ST25R3911 Errata #1.1	Rarely on corrupted frames I_rxs gets signaled but I_rxe is not signaled	Use a SW timer to handle an eventual missing RXE
?
ST25R3911 Errata #1.3	Even though bitrate is going to be detected the bitrate must be set to 106kbps to get correct 106kbps parity
ST25R3911 Errata #1.4	Enable; disable; enable mixer to make sure the digital decoder is in high state. This also switches the demodulator to mixer mode.
ST25R3911 Errata #1.5	Always run the command Calibrate Antenna twice	Always run the command Calibrate Antenna twice
ST25R3911 Errata #1.6	Repetitive I_nre in EMV mode when I_txe is not read	Rarely due to timing reason, the interrupt I_nre repeats several times.
ST25R3911 Errata #1.7	NRE interrupt may be triggered twice	Ignore NRE if is detected together with no Rx Start
ST25R3911 Errata TDB	RXS and NFCT are triggered very close (specially in higher bitrates). If the interrupt status register is being read when NFCT is trigerred, the IRQ line might go low and NFCT is not signalled on the status register.	For initial bitrate detection, mask RXS, only wait for NFCT and RXE.

And for the ST25R3911B:

ST25R3911B Errata #1.1

ST25R3911 may indicate RXS without RXE afterwards, this happens rarely on corrupted frames.

SW timer is used to timeout upon a missing RXE

Can I consider all ST25R3911 errata fixed, excepting the #1.1 ?

Especially because you can fin in the ST25R3911 termination notice (so it's not an old name, but a previous component, pdf attached):

As the ST25R3911 is not meeting new application requirements anymore and already succeeded by ST253911B, the part will not be transferred. The ST25R3911B is the pin compatible replacement with improved performance, errata fixes and is with minor software adjustments fully compatible to ST25R3911.

I focus a lots on this particular subject because as I see 2 NRE irq related errata, I can imagine a 3rd one is possible.

Brian TIDAL · ‎2025-08-06

Hi,

For the Errata Sheet, I cannot do more than recommend you to contact your local ST sales and marketing department to obtain this document.

Regarding the ST25R3911, as explained in the PTN: "The part will not be transferred." Therefore, this device is not part of the ST portfolio.

All silicon workarounds available in the ST25R3911B RFAL code apply to the ST25R3911B.

Rgds

BT

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.