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blank tms320f2808 with reset problems

martin izaak
Prodigy 210 points

Other Parts Discussed in Thread: TMS320F2808

hi forum,

we are working on a project with a tms320f2808 here at the university. the "hot dsp" controls a igtp-six-pack and all worked fine until we disconnected the xds100 after flashing at power on (we had no extra power supply for flashing). after changing the dsp and adding a flash-power supply the dsp resets itself every apr. 7ms. we changed the dsp twice and then we build up a new board with only the dsp (plus power, external reset-ic, ...; but no power stage) - BUT NO CHANGE. so we have three dsps with same behavior, which was sampled from ti. the first one was an older one which we got from our distributor.

any idea about the "self-reset"?

the external reset ic works good, because we have a resistor between dsp and reset ic and the reset comes definitely from the dsp.

thank you for your hints.

martin

  • 0
    TI__Guru* 93800 points

    martin izaak said:

    hi forum,

    we are working on a project with a tms320f2808 here at the university. the "hot dsp" controls a igtp-six-pack and all worked fine until we disconnected the xds100 after flashing at power on (we had no extra power supply for flashing). after changing the dsp and adding a flash-power supply the dsp resets itself every apr. 7ms. we changed the dsp twice and then we build up a new board with only the dsp (plus power, external reset-ic, ...; but no power stage) - BUT NO CHANGE. so we have three dsps with same behavior, which was sampled from ti. the first one was an older one which we got from our distributor.

    any idea about the "self-reset"?

    the external reset ic works good, because we have a resistor between dsp and reset ic and the reset comes definitely from the dsp.

    thank you for your hints.

    martin

    Sounds like the watchdog timer.  It has to be serviced (or disabled) or it will reset the device after 131,072 OSCCLK cycles.  If you have a 20MHz in then this is ~6.5ms.

    Watchdog timer is described in the system control and interrupts guide for a particular device: 

    http://processors.wiki.ti.com/index.php/System_Control_and_Interrupts_Reference_Guides_for_C28x

    -Lori

     

  • 0 in reply to Lori Heustess
    Prodigy 210 points

    hi lori,

    thank you for your fast answer. the device is a blank one, i just get it out of the blister. and i am not able to connect the target. so how can i disable the WD?

    martin

  • 0 in reply to martin izaak
    TI__Guru* 93800 points

    martin izaak said:
    thank you for your fast answer. the device is a blank one, i just get it out of the blister. and i am not able to connect the target. so how can i disable the WD?

    I don't think the watchdog should keep you from connecting but just to make sure, you can put the device in "boot to SCI" mode and see.  This will go to the SCI autobaud routine and just wait - the watchdog is disabled at this point.

    -Lori

  • 0 in reply to Lori Heustess
    Prodigy 210 points

    hi lori,

    thank you for your hint. i put the dsp on the new board into boot sci and the dsp did not reset. so i tryed to flash the dsp over the jtag - which worked!

    so back to the faulty print. there i noticed that the jtag connection faild - after replacing the jtag header this board works fine, too.

    so don´t ask me what happend with this board, a bad header?

    i keep in mind that a blank dsp has a enabled watch dog and the reset every 6.5ms is ok.

    thank you

    martin