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TMS320F28335: Damaging device

Lukas Brzyszkiewicz
Intellectual 335 points
Part Number: TMS320F28335

Hi,

I have big problem with my project.

At random intervals my F28335 have issues with JTAG programming. I have SC_ERR_PATH_BROKEN error and only replacing chip fixes this, so I'm assuming that I have damaged some I/O from JTAG. Sometimes my chip last for few hours, but sometimes for example 10 days. I don't known what is happen. For example - yesterday is working all fine. I've disconnected all cables, turn off all my power. Today I'm turning on power and... JTAG not working with stuck-at-zero or stuck-at-ones error so it again broken my JTAG I/O ??

XCLKOUT is fine and power also. Also I've checked power up sequence - all is OK. Power is on TPS62404DRC-Q1.

Programmer I use is Olimex TMS320-XDS100v3+ rev. C.

I've attached schematics of JTAG signals.

  • 0
    TI__Guru 62975 points
    Lukas,

    Can you scope the JTAG pins while trying to connect or when running a connection test? You might be able to see if a specific signal might be not be reaching required DC voltage levels.

    -Tommy
  • 0 in reply to tlee
    TI__Expert 8105 points
    Lukasz

    You may also try another emulator (if there is one available) just to eliminate the possibility that the emulator is flaky.

    Regards,
    Peter
  • 0 in reply to Peter Galicki
    Intellectual 335 points

    I have three different JTAG emulators (but same model from Olimex). I have four prototyped boards and I already eliminated all problems with programmer, soft, and other. DSP is decisively damaged on JTAG port. Only replacing chip fixes problem.

    Now I'm trying to find the reason of this damages and I don't have any idea. Is this DSP that fragile (plugging in emulator sometimes burn JTAG port?) or I have some non-localized problem on my PCB?

  • 0 in reply to Lukas Brzyszkiewicz
    TI__Expert 8105 points
    Lukas,

    Please make sure that pin 5 of the JTAG header is indeed connected to 3.3V and not 5.0 volts. Otherwise the emulator will drive emulation pins with 5 V and damage the device.

    Next I would suggest isolating whether the problem is with connecting the emulator or the board itself. You can try to power up the board without plugging in the emulator and keep it powered for a day or so. The boot code in the boot ROM will be running and checking the boot pins to see whether to boot from FLASH or some peripheral (like SCI, for example). If it cannot boot, the watchdog will time out and periodically drive a pulse out of the XRSn pin (you can refer to the TRM document for the boot sequence).

    If it fails after running for a while before connecting the emulator - the problem will be with the board. Otherwise, if it doesn't fail running by itself for a long time and then fails when you connect the emulator, the problem will likely be with the emulator.

    Regards,
    Peter