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28335 ePWM Outputs Low on Emulator Connect

Robert Lantzy
Intellectual 360 points

HI,

I've got a 28335 that is controlling an inverter using its ePWM outputs.  Unfortunately, when the emulator connects to the target, the PWM outputs go low for 6ms and then go high and remain there.  That doesn't seem right; but I can't fnd any specific information on what happens when an emulator connect occurs.  Just to be concise, here is the exact set of events that occurs:

  1. Physicaly connect JTAG  (an XDS100v1) to target board.
  2. Power up target. It begins operating (ePWM outputs are now toggling)
  3. Bring up CCSv5.
  4. Command CCS to connect to target (actually, just clock the debug "bug" icon)
  5. Emulator connects, ePWM outputs go low (shorting the inverter output and blownig a fuse), then go high.

After this it is possible to run the target, but the output low glitch is unacceptable for our application. (The PWM outputs are active low, and leaving then low for 6ms causes alot of curent to flow through the IGBT's, blownig the protective fuses.)

I am trying to find out:

  1. Where is this explained?
  2. Is there anything I can do to prevent this?

Thanks,

- Bob

  • 0
    Intellectual 360 points

    Anyone out there who can provide some insight into this problem?

    I've got some additional info:  I tried this with an XDS510 and the problem is the same.  Still getting the 6ms output low glitch upon emulator connect.

    Could there be a bug in the emulator driver in Code Composer?

  • 0 in reply to Robert Lantzy
    TI__Genius 10820 points

    Hi Bob,

    You can use the TBCTL [FREE, SOFT] bit to configure the PWM behavior on emulation events. By "actually, just clock the debug "bug" icon", do you mean you load the program to the micro-controller in addition to connecting CCS to it? You should avoid loading your code while the power stage is powered ON, especially if you are programming on-chip flash.

    I hope this helps.

    Hrishi

     

  • 0 in reply to Hrishi Nene
    Intellectual 360 points

    Hrishi,

    I have tried clicking on the debug "bug" icon, as well as just starting the debug session and then connecting.  I have set the debug configuration to tell the target to reset upon connect, and to reset upno program load.  It seems to do this, but not before allowing the ePWM outputs to toggle at least once.  I would think that a mode would exist to allow the part to go into a known state for debugger connect and/or program load.  That doesn't seem to be the case with this part.

    I'll have to read more about what can be configured via the TBCTL bit, but of course that could only be accomplished after the part was programmed for the first time.  It wouldn't do any good before that, right?

    - Bob