• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 80 subscribers
  • Views 708 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F2801 Repeating XRS result pulse

Richard Shank
Expert 2245 points

I have another repeating XRS pulse output from the processor problem.  This processor was programmed and running but we detected a problem with our power supply not putting out our 20V and +/-15V supply voltages properly so we replaced the transformer.  Now all the supplies are good but the processor is doing constant resets through the XRS pin.  This all started because we have 9 units that all are measuring erratic periods on eCAP1.  We have an older unit that is perfect.

I have attached 3 oscilloscope plots that show the resets are 5us pulses occurring every 10us continuing for 150us to 175us in duration and repeating every 29.3ms.

My objective is to narrow the source of the problem down from 100 pins to something less.  ;^)

Thanks in advance.

  • 0 in reply to Richard Shank
    TI__Expert 7885 points

    Hi Richard,

    Do you have external SVS monitoring the VDDIO and VDD supply rails?  Can you also scope those rails with the XRSn rail?

    Regards,
    Adam

  • 0 in reply to Adam Dunhoft
    Expert 2245 points

    Hi Adam,

    I have scoped the supply at 10ns per division and the resets are not synchronous with any noise on the supply.  Actually, you can see the supply voltage through the pull up in the scope pictures above.  We do have external monitoring on both the 1.8V and 3.3V lines but they feed into an MCP121 which will produce a 100ms reset if tripped.  The inputs to the monitors are also filtered to remove nuisance faults.

    I haven't checked the 1.8V yet but I'm sure it's not kicking off the monitor due to the 100ms reset not being there.  Another reason I don't think this is noise related is it is pretty periodic.  I believe this is something on my board that the processor is seeing that causes it to reset itself.  I don't believe this is due to a processor fault.  I'm also sure it is not a code function problem as we have too many working units.  This is just a new production build and I've got 9 doing the same thing.

    It also very well could be power supply related but I don't understand why it had issues with eCAP1 with a bad transformer and then developed this reset anomaly with a good transformer.  In both cases the 3.3V was 3.3V and stable.  It was only my peripheral supply voltages that were at about 80% of their design value.

  • 0 in reply to Richard Shank
    Expert 2245 points

    Is there anybody out there?....  (Pink Floyd)

  • 0 in reply to Richard Shank
    TI__Expert 7885 points

    Hi Richard,

    The periodic switching of the XRSn pin looks similar to behavior from a watchdog reset, but I would expect that this would continue and not stop.

    The following can be found in the System Control and Interrupts Reference Guide:

    It looks like other than your SVS and the WD, another source of the reset could be your external clock.  Can you scope the clock during these XRSn toggles as well?

    Regards,

    Adam