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Processor Permanently Resetting

Giles Robnson
Expert 1495 points

Other Parts Discussed in Thread: TMS320F28335

Hello,

A few times we have had a processor fail (we believe) in that it appears to be continuously resetting itself. 
The problem has been fixed by replacing the processor in our hardware.

A TMS320F28335 is being used.  Symptoms are:

* Using a Spectrum Digital XDS510USB Emulator, it is not possible to connect at all.
 Various error messages have been displayed, but I forgot to copy any of them and the unit has now gone for repair.

* Monitoring the XRS signal, it is seen to be high most of the time, but it goes low every ~4.2 milliseconds,
 which from the Data Manual (SPRS439M) we take to mean that it’s internal watchdog is causing reset.

The trouble started when I was doing a Flash erase from CCS (5.2.1).  The erase failed due to a timeout, after which connection was impossible.

So
* Is the above assumption of continuous watchdog reset correct?

* Does this mean a broken processor, or is there a way to fix it?

* Any ideas as what could have created the problem?
 We have seen this a few times, and would prefer if it didn’t happen again.

* Is it possible that we have somehow enabled CSM and this is the issue?
 We are not using CSM, so I have no experience of its effects.
 However, my understanding of what I’ve read is that we should still be able to connect
 (presumably that’s needed to unlock).

Any information appreciated.

For what it’s worth, more than one error message has been seen.  At one point CCS was reporting that the wrong
Spectrum Digital drivers were installed, at other times it says "The configured device (TMS320F28335), does not
match the detected device", or something like.

Neither of these reflect the true problem.  Simply swapping the faulty hardware for a new item
(same part number so same processor, etc.) allowed connection and flash programming.

  • 0
    TI__Guru* 93800 points

    Giles Robnson said:
    Monitoring the XRS signal, it is seen to be high most of the time, but it goes low every ~4.2 milliseconds,
     which from the Data Manual (SPRS439M) we take to mean that it’s internal watchdog is causing reset.

    Giles Robnson said:
    * Is the above assumption of continuous watchdog reset correct?

    Giles,

    Yes it sounds like an internal watchdog reset.

    Giles Robnson said:
     Using a Spectrum Digital XDS510USB Emulator, it is not possible to connect at all.
     Various error messages have been displayed, but I forgot to copy any of them and the unit has now gone for repair.

    It's possible the code security module is disconnecting the JTAG.  You can try changing the boot mode to "wait" - this will keep the code running within the boot ROM and thus allow you to connect and debug the part.

    Giles Robnson said:
    The erase failed due to a timeout, after which connection was impossible.

    Giles Robnson said:
     Is it possible that we have somehow enabled CSM and this is the issue?
     We are not using CSM, so I have no experience of its effects.

    Yes - it does sound like the CSM was potentially locked as a result of the erase failure.  If the password is left in an unknown state by the erase algo, then the CSM will be locked.  This is consistent with the JTAG disconnecting and the watchdog resetting the part.  

    Giles Robnson said:
     However, my understanding of what I’ve read is that we should still be able to connect
     (presumably that’s needed to unlock).

    By using the 'wait' boot mode you should be able to connect the JTAG even with the CSM locked.  If you step into protected memory, then the JTAG will drop.

    Giles Robnson said:
    At one point CCS was reporting that the wrong
    Spectrum Digital drivers were installed, at other times it says "The configured device (TMS320F28335), does not
    match the detected device", or something like.

    I'm not sure how to explain this.  CCS 5.2.1 supports all revisions of the 28335.  From one rev to another the PART ID changed, but again this version of CCS supports all of the revisions of this device so that isn't the answer. 

    One thing that can cause flash issues is the VDD3VFL voltage - if this was not healthy or if it was disconnected then the part ID would be reported incorrectly and flash operations would not work properly.

    Regards,

    -Lori

  • 0 in reply to Lori Heustess
    Expert 1495 points

    Lori,

    Many thanks for all this info.  Part has now gone for repair (TMS320 to be replaced), so probably too late to try anything right now, but if we get the problem again (we've had it before), will try what you suggest.

    But what is the 'wait' boot mode ?  SPRS439M Table 3-6 Boot Mode Selection gives 16 modes, but none say anything about wait.

    Regards, Giles

  • 0 in reply to Giles Robnson
    TI__Guru* 93800 points

    Giles Robnson said:

    But what is the 'wait' boot mode ?  SPRS439M Table 3-6 Boot Mode Selection gives 16 modes, but none say anything about wait.

    Regards, Giles

    Giles,

    Oops on this device it is called 'branch to check boot mode'.

    Regards

    Lori

  • 0 in reply to Lori Heustess
    Expert 1495 points

    Lori,

    Thanks again.

    One further question - if the password is left in an unknown state by the erase, does this mean that it is permanently locked and so can never be reprogrammed again?  I assume this is the same as deliberately activating CSM, and then forgetting the password.

    Regards.

     

  • 0 in reply to Giles Robnson
    TI__Intellectual 2720 points

    That's correct Giles.