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JTAG Communication Failures

It is possible to run code on a Stellaris device that causes the device to lose JTAG communication.  The two most common causes are:

  1. Changing the system clock speed to something that the target system does not support.
  2. Changing the function of the Port C[3:0] pins, which are muxed with the JTAG pins.

If you accidentally do either of these things, you can restore communication with your target device by running the Debug Port Unlock utility in LMFlash Programmer as shown below.  Select the appropriate product class for your device.  If you don't know the class for your device, you can find it by reading the Device Identification 0 (DID0) register at address 0x400F.E000.  Then click on the "Unlock" button.

On Tempest- and Firestorm-class devices, the MAC address is erased by the Debug Port Unlock utility, so be sure to write down the number before running the utility.

Regards,

Sue

36 Replies

  • In reply to gkonzak:

    Thank you very much.

    The best regards.

    Andrzej M.

  • In reply to gkonzak:

    Hi gkonzak,

    There is the red circle on XDS 100 v2ARM emulator and it is connected with red cable (10 pin).

     

    There is white triangle on MDL –ADA2 adapter from RDK-IDM-L35 – Stellaris with red cable(10pin).

    and on the from RDK-IDM-L35 – Stellaris board there is the same white triangle

     

     

    Can I connect red circle from xds100 v2 (Blackhawk)  with white triangle from froit m RDK-IDM-L35 – Stellaris?

    Is it the +3,3 V?

     

    The best regards.

    Andrzej M

  • In reply to Andrzej Maciejewski:

    The triangle indicates pin 1, and it does usually have 3.3V on it.

  • In reply to gkonzak:

    I know it . But if is it the same white triangle in Texas Instrument (Austin) and red circle in  Blackhawk ( New york)?

    Texas Instruments

    Blackhawk

    The best  regards.

    Andrzej M.

  • In reply to Andrzej Maciejewski:

    I have never used Blackhawk. A TI person could answer that.

  • hello, i have a TM4C123GXL launchpad and as I am new user, I programmed port C pins as out puts and now facing the problem. can my problem be solved using this method ? please help me I don't know much about these things..

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