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Would isolated JTAG help with "Power Failure on Target CPU"

Todd Anderson78572
Guru 14640 points
Other Parts Discussed in Thread: OMAP-L138, OMAPL138

Reference: e2e.ti.com/.../104344

Would the isolated JTAG connector also help with this?

If so, is there one isolated JTAG that is "more recommended?"

(I know that isolating the PC from the target board helps, but that is not always possible...)

I am using Code Composer Studio 6.1.1, XDS100v2, on OMAP-L138-EP processor.

Full error: "C674x_0: Power Failure on Target CPU"

  • 0
    TI__Guru**** 171349 points

    Todd,

    In the case described in the attached thread, the solution was interrupting the current flow of the ground loop via an isolation transformer. Your question touches the same concept - i.e., the JTAG isolated connector will also interrupt the current flow of the ground loop. Obviously this is only true if JTAG is the only thing you have connected between the target board and the PC - don't forget you may have other ports (RS232, RS485, anything parallel, etc.).

    I don't have a "recommended" model per se, but we have in our estore an ISO adapter for the TI 14-pin standard (TMDSADP1414-ISO), but Blackhawk has other options.

    Hope this helps,

    Rafael

  • 0 in reply to desouza
    Guru 14640 points
    Unfortunately the ISO adapter only goes to 3.3 volts, and the OMAP-L138 JTAG is 1.8 volts. I suppose a voltage translation circuit could be added to the target board to allow for 3.3 volts at the JTAG header, which would then allow the ISO adapter to work...
  • 0 in reply to Todd Anderson78572
    TI__Guru**** 171349 points

    Todd,

    I am not sure where you got the JTAG voltage of the OMAPL138, as I can't seem to find anything clearly specified in its datasheet.

    That said, this device is fully compatible with 3.3v-only JTAG debuggers such as Spectrum Digital's XDS510USB (not plus) and Blackhawk's old USB560 (not m or bp). I have been using my boards for years now without any connection issue or damage.

    Regards,

    Rafael

  • 0
    Mastermind 9125 points
    Recently, I just bought a "XDS220 ISO JTAG" from SpectrumDigital. ISO is helpful if your target connects to power supply with the EARTH pin connected. If your target is using battery then no difference.

    The major protection is to prevent improper probe (of oscilloscope) connection. If the ground of probe is connected to a non-ground point in your target, you may create a ground loop issue and some components will get burned. It could be your target board, your oscilloscope, your power supply or your PC. Oscilloscope and power supply are usually very "strong". So, either target board or PC will get burned. An ISO JTAG will at least protect your PC.

    And as desouza said, if you have other ground connections between PC and target board. The isolation won't work.
  • 0 in reply to Robert Chen
    Guru 14640 points
    Has anyone tried the 14-pin standard or Blackhawk with the OMAP-L138 LCDK?
    It is 3.3 volts, and as far as I know, the ISO should plug in and work --- but it doesn't --- on several of the LCDKs that are in house.

    I plan to bring in another board from home to try it against, just to make sure it is not the ISO.
  • 0 in reply to Todd Anderson78572
    Mastermind 9125 points

    Unfortunately I don't have OMAP on hand to test the ISO connection.

  • 0 in reply to Robert Chen
    Guru 14640 points
    I was able to verify that the Isolated JTAG did work with a C6713DSK and XDS560 emulator. Not sure why it has problems with the OMAP-L138 LCDK...
  • 0 in reply to Todd Anderson78572
    Guru 92251 points

    Todd Anderson78572 said:
    I was able to verify that the Isolated JTAG did work with a C6713DSK and XDS560 emulator. Not sure why it has problems with the OMAP-L138 LCDK...

    I don't have an isolated JTAG to investigate, but one possible difference between the C6713DSK and OMAP-L138 LCDK is that the OMAP-L138 has an ARM926 which requires adaptive clocking.

    Does the Isolated JTAG support adaptive clocking?

    Also, what are the symptoms of the problems with the OMAP-L138 and isolated JTAG? From memory if the problem is due to adaptive clocking not being enabled then the connection will be intermittent.