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Power loss on target error

Makarand Deshmukh
Prodigy 220 points
Other Parts Discussed in Thread: TM4C123AE6PM

Hello,

I am using a Tiva Tm4C123AE6PM uC with CCS 6 and XDS100v2. 

When I connect a debugger to my custom board, I get an error saying target has no power (-180). I have connected the power and can see the voltages correct on a multimeter. 

When I try programming another board from the same debugger and CCS, it does that correct. 

Both the boards are identical as far as the processor and the 3v3 sections are concerned. Please advise what can be done. 

The new boards, which are not being programmed, we have just received them from the manufacturing process.

Please help.

Thanks,

Makarand

  • TI__Guru**** 171104 points

    Makarand,

    The power loss error is explained in the thread below, and may still be seen as such even if power is present on the board. Check:
    e2e.ti.com/.../1070089

    Hope this helps,
    Rafael

  • in reply to desouza
    Prodigy 220 points
    Hi Rafael,

    Thank you.

    I checked the voltage on the VTref pin on the debugger and it is 3.08 volts. It still says power loss.

    Thanks,
    Makarand
  • in reply to Makarand Deshmukh
    TI__Guru**** 171104 points
    Makarand,

    Would you mind copying the output text of the "test connection" button to a .txt file and attaching to this post? I just want to be absolutely sure we are talking about the very same error. Also, if the "test connection" does not show an error, can you send me a screenshot of the CCS screen?

    Given the same debugger works on another environment, I can't help but suspect something on the board is causing this, as the voltage detect threshold on the XDS100v2 is about 1.6V.

    I am pretty sure you already did this, but perhaps a voltage comparison between the working and non-working boards may help. Also, I wonder if somehow the core itself is not properly powered, despite the voltage is present on the device pin - in other words, the device itself may be faulty. Although this would throw a different error message than I believe previously, thus the screenshot and the test connection error would help with this.

    Unfortunately JTAG can only "see" so far into the system, therefore something that is caused by other factors may be perceived by the JTAG as having a different cause.

    Regards,
    Rafael
  • in reply to desouza
    Prodigy 220 points

    Hi Rafael,

    Here is the screen shot from CCS and the notepad file, Please check.

    Also, I have already tested the voltages on the two boards. They are not different than a few milivolts.

    The core voltage on the board which is failing to program is 1,2V.

    Thanks!

    Makarand

  • in reply to Makarand Deshmukh
    TI__Guru**** 171104 points

    Makarand,

    Thank you for the additional information, especially the last paragraph. XDS100-class debuggers are rated to operate as low as 1.8V. In other words, below this anything can happen (even work!), but I wouldn't rely on that.

    In this case, I would imagine that a specific "programming mode" jumper, microswitch or a small circuitry would have to be hardwired to the newer boards so it would raise the voltage of the device only for programming.  

    Although costly, another possibility is to invest in a XDS560v2-class JTAG debugger, which is rated down to 1.2V. If you would like to pursue this alternative, I would try to borrow one for a limited time (perhaps from your local TI sales office) and make sure it works fine with your existing hardware, as you are operating in the limits of operation.  

    There is another less costly alternative (a XDS200-class JTAG debugger), but this goes down to 1.4V.

    Hope this helps,

    Rafael

  • in reply to desouza
    Prodigy 220 points
    Hi Rafael,

    Thank you for the input. Although I must say that I have used XDS100v2 for about two years now (earlier with Stellaris and now with Tiva) and have never faced such an issue.

    This leads me into thinking that it might be something else.

    Can the core voltage play a part in this? If yes, then how? Because, I think if the debugger gets higher than 1.8 volts at the VTARG signal, then it assumes that the target is connected, isn't that correct? The voltage at VTARG is 3.1V.

    And also an old board with the exact same JTAG circuitry and power supply works perfectly with the debugger.

    I have verified all the pins and connections to the debugger and all seems to be correct.

    Thanks,
    Makarand
  • in reply to Makarand Deshmukh
    Guru 92251 points

    Makarand Deshmukh said:
    Can the core voltage play a part in this?

    On a TM4C123AE6PM the I/O voltage for the JTAG pins is VDD which in nominally 3.3V.

    Therefore, the (lower) VDDC core voltage doesn't play a part in the error you are seeing.

    [I am unsure of what is causing the error]