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Bus off state

Chris Hauxwell

Hi,

 

I have a question regarding the operation of CAN devices in the bus off state. By “bus off” I mean the state a CAN device enters after “Error passive”.

 

If a node goes “Bus off” whilst trying to transmit a message, what happens to the message being transmitted? Does it remain in the transmit buffer until the CAN device becomes Error Passive, then is transmitted? I wondering if CAN messages could be lost due to a transmitting device entering Bus Off.

 

Thanks

Chris Hauxwell

 
 
Chris Hauxwell
Software Manager
 
Sevcon Ltd
Kingsway South, Gateshead, NE11 0QA
England
 
Direct  +44 (0)191 497 9161
Fax     +44 (0)191 482 4223
Email   [hidden email] 
Web    www.sevcon.com
                                      

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Sevcon LimitedRegistered Office: Kingsway South, Gateshead, NE11 0QA; Registered No. 500106 England; Vat No GB 178546912.

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Re: Bus off state

Ulrik Hagström
Chris,

In order go from state "ERROR PASSIVE" to "BUS OFF" the last message being
sent did not get the ACK-bit set and the error counter exceeded the value
255. This message should not be accepted by any of the nodes on the bus -
I guess that is clear.

A CAN-controller that has entered "BUS OFF" can not automatically enter
"ERROR PASSIVE" state again - you actively need to re-initiate it back to
ERROR ACTIVE ("BUS ON") - guess that is clear too.

You question boils down to the CAN-controller being used. I would guess
that most of the CAN controllers automatically clears their TX-buffers in
such operation (reinitiate, go bus on), or you should do that youself to
be in total control on what is being sent (the data in the CAN message is
maybe old) on the bus when reiniating the CAN-controller that went bus
off.


Best Regards,

Ulrik

http://www.canopen.nu




> Hi,
>
>
>
> I have a question regarding the operation of CAN devices in the bus off
> state. By "bus off" I mean the state a CAN device enters after "Error
> passive".
>
>
>
> If a node goes "Bus off" whilst trying to transmit a message, what
> happens to the message being transmitted? Does it remain in the transmit
> buffer until the CAN device becomes Error Passive, then is transmitted?
> I wondering if CAN messages could be lost due to a transmitting device
> entering Bus Off.
>
>
>
> Thanks
>
> Chris Hauxwell
>
>
>
> Chris Hauxwell
>
> Software Manager
>
> Sevcon Ltd
> Kingsway South, Gateshead, NE11 0QA
> England
>
> Direct  +44 (0)191 497 9161
> Fax     +44 (0)191 482 4223
> Email  [hidden email]
> Web    www.sevcon.com
>
>
>
> This e-mail contains confidential and/or privileged information. If you
> are not the intended recipient (or have received this e-mail in error)
> please notify the sender immediately and destroy this e-mail. Any
> unauthorized copying, disclosure or distribution of the material in this
> e-mail is strictly forbidden.
>
> Diese E-Mail enthalt vertrauliche und/oder rechtlich geschutzte
> Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail
> irrtumlich erhalten haben, informieren Sie bitte sofort den Absender und
> vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte
> Weitergabe dieser Mail ist nicht gestattet.
>
> Les informations figurant sur cet e-mail ont un caractere strictement
> confidentiel et sont exclusivement adressees au destinataire mentionne
> ci-dessus. Tout usage, reproduction ou divulgation de cet e-mail est
> strictement interdit si vous n'en etes pas le destinataire. Dans ce cas,
> veuillez nous en avertir immediatement par la meme voie et detruire
> l'original. Merci.
>
> Sevcon LimitedRegistered Office: Kingsway South, Gateshead, NE11 0QA;
> Registered No. 500106 England; Vat No GB 178546912.
>




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AW: Bus off state

"Christian Bräutigam"-2
In reply to this post by Chris Hauxwell

Chris,

 

A “bus off” state in a CAN controller regularly requires software interaction in order to be changed towards a communicating state.

CAN controllers’ state machines may never return automatically to an error passive state. Thus, it is up to the software anyway to handle this bus-off situation and resend  the message in question later.

 

I hope that helps.

 

best regards

 

Christian   

 

Christian Bräutigam
Product Manager Industrial Communication

Softing AG
Richard-Reitzner-Allee 6
D-85540 Haar
Tel. +49 (0) 89 456 56-328
Fax +49 (0) 89 456 56-399

Softing AG, Richard-Reitzner-Allee 6, D-85540 Haar, Internet: http:// www.softing.com
Softing Aktiengesellschaft: Vorsitzender des Aufsichtsrates: Dr. Horst Schiessl; Vorstand: Dr. Wolfgang Trier (Vorsitzender), Dr. Michael Siedentop
Sitz: Haar bei München,
Amtsgericht München, HRB 127 604, USt-ID: DE186893974 WEEE Reg. Nr. DE 39257114


Von: [hidden email] [mailto:[hidden email]] Im Auftrag von Chris Hauxwell
Gesendet: Donnerstag, 18.
Juni 2009 10:24
An: [hidden email]
Betreff: [CANLIST] Bus off state

 

Hi,

 

I have a question regarding the operation of CAN devices in the bus off state. By “bus off” I mean the state a CAN device enters after “Error passive”.

 

If a node goes “Bus off” whilst trying to transmit a message, what happens to the message being transmitted? Does it remain in the transmit buffer until the CAN device becomes Error Passive, then is transmitted? I wondering if CAN messages could be lost due to a transmitting device entering Bus Off.

 

Thanks

Chris Hauxwell

 

 

Chris Hauxwell

Software Manager

 

Sevcon Ltd

Kingsway South, Gateshead, NE11 0QA

England

 

Direct  +44 (0)191 497 9161

Fax     +44 (0)191 482 4223

Email   [hidden email] 

Web    www.sevcon.com

                                      

This e-mail contains confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.

Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet.

Les informations figurant sur cet e-mail ont un caractère strictement confidentiel et sont exclusivement adressées au destinataire mentionne ci-dessus. Tout usage, reproduction ou divulgation de cet e-mail est strictement interdit si vous n'en êtes pas le destinataire. Dans ce cas, veuillez nous en avertir immédiatement par la même voie et détruire l'original. Merci.

Sevcon LimitedRegistered Office: Kingsway South, Gateshead, NE11 0QA; Registered No. 500106 England; Vat No GB 178546912.

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RE: Bus off state

Chris Hauxwell

OK. Thanks.

 

The DSP I’m using (Texas Instruments 281x) has a feature to automatically return to Error Passive from Bus Off after 128*11 recessive bits are seen. I guess then my question about what happens to a transmitted message after bus off is really a device specific question.

 

Regards

Chris

 

From: [hidden email] [mailto:[hidden email]] On Behalf Of "Christian Bräutigam"
Sent: 18 June 2009 12:28
To: [hidden email]
Subject: AW: [CANLIST] Bus off state

 

Chris,

 

A “bus off” state in a CAN controller regularly requires software interaction in order to be changed towards a communicating state.

CAN controllers’ state machines may never return automatically to an error passive state. Thus, it is up to the software anyway to handle this bus-off situation and resend  the message in question later.

 

I hope that helps.

 

best regards

 

Christian   

 

Christian Bräutigam
Product Manager Industrial Communication

Softing AG
Richard-Reitzner-Allee 6
D-85540 Haar
Tel. +49 (0) 89 456 56-328
Fax +49 (0) 89 456 56-399

Softing AG, Richard-Reitzner-Allee 6, D-85540 Haar, Internet: http:// www.softing.com
Softing Aktiengesellschaft: Vorsitzender des Aufsichtsrates: Dr. Horst Schiessl; Vorstand: Dr. Wolfgang Trier (Vorsitzender), Dr. Michael Siedentop
Sitz: Haar bei München,
Amtsgericht München, HRB 127 604, USt-ID: DE186893974 WEEE Reg. Nr. DE 39257114


Von: [hidden email] [mailto:[hidden email]] Im Auftrag von Chris Hauxwell
Gesendet: Donnerstag, 18.
Juni 2009 10:24
An: [hidden email]
Betreff: [CANLIST] Bus off state

 

Hi,

 

I have a question regarding the operation of CAN devices in the bus off state. By “bus off” I mean the state a CAN device enters after “Error passive”.

 

If a node goes “Bus off” whilst trying to transmit a message, what happens to the message being transmitted? Does it remain in the transmit buffer until the CAN device becomes Error Passive, then is transmitted? I wondering if CAN messages could be lost due to a transmitting device entering Bus Off.

 

Thanks

Chris Hauxwell

 

 

Chris Hauxwell

Software Manager

 

Sevcon Ltd

Kingsway South, Gateshead, NE11 0QA

England

 

Direct  +44 (0)191 497 9161

Fax     +44 (0)191 482 4223

Email   [hidden email] 

Web    www.sevcon.com

                                      

This e-mail contains confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.

Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet.

Les informations figurant sur cet e-mail ont un caractère strictement confidentiel et sont exclusivement adressées au destinataire mentionne ci-dessus. Tout usage, reproduction ou divulgation de cet e-mail est strictement interdit si vous n'en êtes pas le destinataire. Dans ce cas, veuillez nous en avertir immédiatement par la même voie et détruire l'original. Merci.

Sevcon LimitedRegistered Office: Kingsway South, Gateshead, NE11 0QA; Registered No. 500106 England; Vat No GB 178546912.

 
 
Chris Hauxwell
Software Manager
 
Sevcon Ltd
Kingsway South, Gateshead, NE11 0QA
England
 
Direct  +44 (0)191 497 9161
Fax     +44 (0)191 482 4223
Email   [hidden email] 
Web    www.sevcon.com
                                      

This e-mail contains confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.

Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet.

Les informations figurant sur cet e-mail ont un caractère strictement confidentiel et sont exclusivement adressées au destinataire mentionne ci-dessus. Tout usage, reproduction ou divulgation de cet e-mail est strictement interdit si vous n'en êtes pas le destinataire. Dans ce cas, veuillez nous en avertir immédiatement par la même voie et détruire l'original. Merci.


Sevcon LimitedRegistered Office: Kingsway South, Gateshead, NE11 0QA; Registered No. 500106 England; Vat No GB 178546912.

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From: [hidden email] [mailto:[hidden email]] On Behalf Of Chris Hauxwell
Sent: Thursday, June 18, 2009 8:17 AM
To: [hidden email]
Subject: RE: [CANLIST] Bus off state

 

OK. Thanks.

 

The DSP I’m using (Texas Instruments 281x) has a feature to automatically return to Error Passive from Bus Off after 128*11 recessive bits are seen. I guess then my question about what happens to a transmitted message after bus off is really a device specific question.

 

Regards

Chris

 

From: [hidden email] [mailto:[hidden email]] On Behalf Of "Christian Bräutigam"
Sent: 18 June 2009 12:28
To: [hidden email]
Subject: AW: [CANLIST] Bus off state

 

Chris,

 

A “bus off” state in a CAN controller regularly requires software interaction in order to be changed towards a communicating state.

CAN controllers’ state machines may never return automatically to an error passive state. Thus, it is up to the software anyway to handle this bus-off situation and resend  the message in question later.

 

I hope that helps.

 

best regards

 

Christian   

 

Christian Bräutigam
Product Manager Industrial Communication

Softing AG
Richard-Reitzner-Allee 6
D-85540 Haar
Tel. +49 (0) 89 456 56-328
Fax +49 (0) 89 456 56-399

Softing AG, Richard-Reitzner-Allee 6, D-85540 Haar, Internet: http:// www.softing.com
Softing Aktiengesellschaft: Vorsitzender des Aufsichtsrates: Dr. Horst Schiessl; Vorstand: Dr. Wolfgang Trier (Vorsitzender), Dr. Michael Siedentop
Sitz: Haar bei München,
Amtsgericht München, HRB 127 604, USt-ID: DE186893974 WEEE Reg. Nr. DE 39257114


Von: [hidden email] [mailto:[hidden email]] Im Auftrag von Chris Hauxwell
Gesendet: Donnerstag, 18.
Juni 2009 10:24
An: [hidden email]
Betreff: [CANLIST] Bus off state

 

Hi,

 

I have a question regarding the operation of CAN devices in the bus off state. By “bus off” I mean the state a CAN device enters after “Error passive”.

 

If a node goes “Bus off” whilst trying to transmit a message, what happens to the message being transmitted? Does it remain in the transmit buffer until the CAN device becomes Error Passive, then is transmitted? I wondering if CAN messages could be lost due to a transmitting device entering Bus Off.

 

Thanks

Chris Hauxwell

 

 

Chris Hauxwell

Software Manager

 

Sevcon Ltd

Kingsway South, Gateshead, NE11 0QA

England

 

Direct  +44 (0)191 497 9161

Fax     +44 (0)191 482 4223

Email   [hidden email] 

Web    www.sevcon.com

                                      

This e-mail contains confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.

Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet.

Les informations figurant sur cet e-mail ont un caractère strictement confidentiel et sont exclusivement adressées au destinataire mentionne ci-dessus. Tout usage, reproduction ou divulgation de cet e-mail est strictement interdit si vous n'en êtes pas le destinataire. Dans ce cas, veuillez nous en avertir immédiatement par la même voie et détruire l'original. Merci.

Sevcon LimitedRegistered Office: Kingsway South, Gateshead, NE11 0QA; Registered No. 500106 England; Vat No GB 178546912.

 

 

Chris Hauxwell

Software Manager

 

Sevcon Ltd

Kingsway South, Gateshead, NE11 0QA

England

 

Direct  +44 (0)191 497 9161

Fax     +44 (0)191 482 4223

Email   [hidden email] 

Web    www.sevcon.com

                                      

This e-mail contains confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.

Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet.

Les informations figurant sur cet e-mail ont un caractère strictement confidentiel et sont exclusivement adressées au destinataire mentionne ci-dessus. Tout usage, reproduction ou divulgation de cet e-mail est strictement interdit si vous n'en êtes pas le destinataire. Dans ce cas, veuillez nous en avertir immédiatement par la même voie et détruire l'original. Merci.


Sevcon LimitedRegistered Office: Kingsway South, Gateshead, NE11 0QA; Registered No. 500106 England; Vat No GB 178546912.

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