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SJA1000 Error Counters

Hello,

I need some more detailed information about how *exactly* the error counters of the SJA1000 (in BasicCAN mode) are working.

The datasheet only tells me that if the transmit error counter overflows (after 256 errors), the device will stop all bus activities until it's reactivated under software control. There seems to be no information about

- which conditions *exactly* cause increments of that error counter;

- if the error counter reset or decremented again upon success transmit;

- can the error counter be cleared under software control by any means;

- receive error counting; etc.

Unfortunately, though this is a mature chip and in full production for several years now, additional information at the Philips homepage becomes less instead of more - several application notes obviously vanished, and the only one that is still there is of 1997.

The SJA1000 is used in BasicCAN mode in the current application, not in PeliCAN mode. There are more detailed tables about error conditions and their effect on the error counters in the PeliCAN- specific section of the application note (AN 97076). Nothing like this is mentioned on the pages about BasicCAN - do these tables also apply to BasicCAN, though they explicitly are in the PeliCAN section?

Thanks for any hints or links that can shed some light on this...

--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
http://www.autometer.de
Reply to
Tilmann Reh
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the errors that cause counters increment are parts of the CAN specification itself, see

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for example (p25).

The "official" errors are described p24.

I do not know if you can reset the error counter by software on this chip but I've seen on Fujitsu µC for example that the error counters can not be modified by the software. That's one reason why some CAN controllers now integrates a listen-only mode in order to:

- not to send ACK on the bus

- not to care about errors on the bus (and do not go into a bus off mode)

Nevertheless, a bus off state does not mean no RX (at least no TX or ACK)!

Does it fit to your question?

Mouarf

"Tilmann Reh" schrieb im Newsbeitrag news:cp79fv$hjv$ snipped-for-privacy@online.de...

Reply to
Mouarf

Did you see the notice that points you at an other controller the SJA1000 in BasicCAN mode is designed to be compatible to? Odds are, what isn't described in SJA1000_3.pdf, you'll find in that controller's datasheet.

IIRC, most of that is documented in the CAN spec itself already, which see.

--
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.
Reply to
Hans-Bernhard Broeker

I don't have the specific information you want, but I remember this: The error count is decremented a little every time you get ( or send ??) a message successfully, so there is no need to manually reset the counter. If you fix your error condition, after a certain amount of traffic the chip forgets there ever were any errors. Of course, you could always re-initialize the whole chip.

--
     o__      |  Paul Probert
     ,>/'_    |  Associate Scientist
    (_)\(_)   |  The University of Wisconsin-Madison
              |  Dept. of Electrical and Computer Engineering
Reply to
Paul Probert

Mouarf schrieb:

Thanks for the link. I intended to search the original specification anyways... However, what I really was/am wondering about is the fact that this behaviour is similarly described in the SJA1000 application note - without the decrementing conditions, and only for PeliCAN mode, however.

But if a device enters bus off state, it will not respond to anything on the bus. (Passive and active error states are described in the documents about the SJA1000, but no exact rules about how the error counters are behaving in BasicCAN mode...)

Partly. :-) Many thanks,

--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
http://www.autometer.de
Reply to
Tilmann Reh

Hans-Bernhard Broeker schrieb:

I know the predecessor, the 82C200. Unfortunately, I started CAN development in 1997 when the SJA1000 just came out - so I used that one right from the start, and I don't have the 82C200 datasheet or related application notes. Unfortunately, these also obviously vanished from the web - I did not find any detailed reference or the datasheet.

If you have it, I would be lucky if you could send it by mail.

Yes - but the SJA1000 data sheet and/or application notes should contain the exact implementation details anyway. What still puzzles me is the mentioning of all error handling details only for PeliCAN mode...

Thanks,

--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
http://www.autometer.de
Reply to
Tilmann Reh

Paul Probert schrieb:

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your

were

From the CAN specification, this should be true. I was missing the exact implementation details for the SJA1000 in its datasheet or application note...

Thanks,

--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
http://www.autometer.de
Reply to
Tilmann Reh

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Anyway, I don't think you really need the 82C200 datasheet. Scanning over the SJA100_3.pdf, I saw a short notice that essentially said that in BasicCAN mode, its error counters behave exactly as specified in the CAN spec itself. Given that you don't get to read them out in this mode, anyway, that's about all you'll ever know about it.

That you'll have to bring to Philips' attention, not ours. ;-)

OTOH, if you think this through to conclusion, requiring this would mean every CAN device's documentation would have to include a verbatim copy of large parts of the CAN spec --- that can't really be useful, and might even be impossible: the official CAN spec (ISO-whatever) costs money.

Describing the BasicCAN mode of the SJA1000 as "same as 82C200, with the following changes:" probably made sense back when the SJA1000 datasheet was written, but not any longer. Not unless they keep the

82C200 one available, that is.

That's because PeliCAN is more complex, and implements lots of things that aren't covered by the CAN spec, and thus have to be documented explicitly rather than by reference.

--
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.
Reply to
Hans-Bernhard Broeker

Hans-Bernhard Broeker schrieb:

This is interesting... I searched for "82c200" only, and got no useful hit - however, there were some notes on CAN homepages mentioning that the 82C200 datasheet was not available... (Perhaps I should inform those webmasters about the link you provided. :-) )

Thanks!

OK, I can agree to that.

Thanks for your help.

--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
http://www.autometer.de
Reply to
Tilmann Reh

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