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TMS320F28377D system clock setting

Robert S
Prodigy 20 points
Other Parts Discussed in Thread: CONTROLSUITE, TMS320F28377D

Hallo everyone,

I am working with the TMS320F28377D and just tried some of the example projects I found in the controlSUITE. In the file F2837xD_SysCtrl.c there is the function InitSysCtrl() with the line:

InitSysPll(XTAL_OSC,IMULT_20,FMULT_1,PLLCLK_BY_2); 		//PLLSYSCLK = 10Mhz(OSCCLK) * 40 (IMULT) * 1 (FMULT) /  2 (PLLCLK_BY_2)

The value of IMULT in the function call does not fit to the value in the comment. Does this mean, the microcontroller is running with 100MHz instead of 200MHz?

I called InitSysPll with IMULT_40 and tried to run the project blinky_dc_cpu01. But that did not work.

I hope you can help me.

Yours,

Robert
 

  • 0
    TI__Guru 61235 points

    Robert,

    The comment is wrong.  If you look at the function call, it is passing XTAL_OSC.  This means crystal oscillator, not internal 10 MHz oscillator.  Basically, the function call is assuming a 20 MHz external crystal on the oscillator inputs.  Multiply by 20 and then divide by 2, and you're running at 200 MHz.  The F28377D ControlCard has a 20 MHz crystal on it.

    Regards,

    David

  • 0
    TI__Guru** 109155 points

    Hi Robert,

    With the given code, device should be running @100MHz. You could also bring out the SYSCLKOUT on GPIO pin and measure the frq to confirm the same.

    Are you running the given progect from Flash? If yes then while changing the device operating frq, one also need to change the Flash wait state inside InitFlash() function.

    Regards,

    Vivek Singh

  • 0 in reply to Vivek Singh
    TI__Guru** 109155 points

    Robert,

    As David mentioned, if you are using XTAL_OSC frq of 20MHz then device will be running @200 MHz. It depends on what XTAL_OSC frq you are using.

    The highlighted code in comment is with INT_OSC which is by default 10MHz on this device.

    Regards,

    Vivek Singh

  • 0 in reply to Vivek Singh
    Prodigy 20 points

    Hallo David and Vivek,

    I get it now. Thank you very much for your fast reply! I really appreciate that.

    Regards,

    Robert