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Original question:

JTAG error: Unable to access the DAP

TMS570LS3137: Unable to access the DAP

Mark Blay
Intellectual 370 points
Part Number: TMS570LS3137

I am seeing exactly the same issue as described in the linked thread.

I have 3 TMS570LS3137 devices that are all 'locked' in this way.

I follow the steps described to unlock the device but have not been successful.

There appear to be many forum threads relating to this issue, but none reaches a conclusion that helps me.

Please advise.

  • 0
    TI__Guru**** 196596 points

    Hello Mark,

    Can you try the following:

    1. From the View menu in CCS open the Target Configuration View
    2. Find the .ccxml file that is part of your project
    3. Right click on it and choose "Launch selected configuration".  This will start a debug session in CCS but won't connect to anything yet.
    4. When the debug view opens click on the top level node in the tree (it will be the name of the .ccxml file).  Select "Show all cores".
    5. Under "Non debuggable devices" select the one that ends in ICEPick_C.
    6. Click on the connect button on the toolbar. 
    7. Open the registers view.
    8. If you expand core registers. Do the TAP registers have values other than 0 or 1?
    9. Next select the DAP under "Non debuggable devices" and see if you can connect to that.

  • 0 in reply to QJ Wang
    Intellectual 370 points

    Hi QJ, thanks for your response.

    I am happy to say we resolved the issue today :).

    I followed the steps previously posted, similar to those above, and eventually was able to manually assert nRST while hitting 'Retry' after failed attempts to connect to the target in CCS. The key was to disable the external oscillator, causing the TMS570 to use the LPO which gave significantly longer before the loaded code hit the exception and made timing of the reset easier to achieve.

    Thanks again,

    Mark.