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A strange question about TMS320F2809: The external clock DOES functions, but no output on XCLKOUT?

hong lin14085
Prodigy 50 points

Other Parts Discussed in Thread: TMS320F2809, TMS320F2806

Hello:

My system: TMS320F2809  + an external oscillator of 20MHz / 3.3V

1) The output of external oscillator is tied to XCLKIN, and X1 is tied to GND.

2) The program has already been donwload to FLASH.

3) Mostly the program runs correctly after powered-up, sometimes It seems that the program does NOT start. Then I tested the following signals:

   -  XCLKIN : 20MHz

   - XCLKOUT: No output on this pin.

I suspect that, maybe, the DSC detected a "Main Oscillator Fail Detection". Then I did the following test  in my initializing codes:

   if (SysCtrlRegs.PLLSTS.bit.MCLKSTS != 0)
   {
      EALLOW;
      GpioCtrlRegs.GPAMUX1.all = 0x00000000;  // All GPIO
      GpioCtrlRegs.GPAMUX2.all = 0x00000000;  // All GPIO
      GpioCtrlRegs.GPAMUX1.all = 0x00000000;  // All GPIO
      GpioCtrlRegs.GPADIR.all = 0xFFFFFFFF;   // All outputs
      GpioCtrlRegs.GPBDIR.all = 0x0000000F;   // All outputs
      EDIS;
      GpioDataRegs.GPADAT.all = 0x5A5A;  /* The relative IO pin is tied to a LED */
      GpioDataRegs.GPBDAT.all = 0x005A;  /* The relative IO pin is tied to a LED */
      while(1) ;
      SysCtrlRegs.PLLSTS.bit.MCLKCLR = 1;
      asm("        RESET");       // for debug only???????
     //asm("          TRAP #0");
      //while(1);
   }

But the relatie LEDs are not the desired status.

I'm appreciated if any one would help me to solve this problem. Thank you in Advace.

Larry.

 

 

  • 0
    Genius 5885 points

    Hi Larry!

    Check the errata at http://www.ti.com/litv/pdf/sprz171k. There is a silicon bug in first revisions of 2809, which can cause described behavior

     

    Regards, Mitja

  • 0 in reply to Mitja Nemec
    Prodigy 50 points

    Hi Mitja,

    Thank you for your help! :)

    I checked the errata and are testing now. I will report the final result ASAP.

  • 0 in reply to hong lin14085
    Prodigy 50 points

    Hi Mitja,

    I changed the TMS320F2809 from silicon verion 0 to version 1. The system runs very well. Thank you for your kind and efficient help again.

    Best regards,

    Larry

  • 0 in reply to Mitja Nemec
    Intellectual 575 points

    This is not exactly a timely reply, but perhaps someone will see this and answer my question.

    I have a similar problem with the TMS320F2806.  Now there are no errata for this issue on the 2806, but the particular erratum for the 2809 Rev 0 says:

    "First silicon release. (This is functionally equivalent to Revision C of the TMS320F280x silicon.)"

    So if I am using Rev C of the 2806, is it reasonable to suppose that this issue exists there also?

    I would also add the observation that after 2-3 seconds, the time is exactly repeatable for any given unit, XCLKOUT appears and the DSP starts running code, not in limp mode, but with MCLKSTS set, and with SYSCLK=OSCCLK/2.   It is as if a missing clock reset occurred, but after a very long time, much longer than the 13-bit VCOCLK operating at Limp Mode frequency.  Is this a known phenomenon? Can I depend on it to get my code running, after a few seconds of delay, without performing hardware changes?