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CPU clock configuration?

Marko S
Intellectual 670 points
Other Parts Discussed in Thread: OMAP-L138, OMAPL138, SYSBIOS

I'm wondering about how the clock configuration is done in SYS/BIOS6.

If I have a 24MHz reference clock, how do the SYS/BIOS know that? Where do I adjust that parameter?

I only find CPU clock frequency (Hz) setting under Platform Settings.

 

  • 0
    TI__Mastermind 18320 points

    Marko,

    The platform is indeed where the input clock frequency should be accounted for. 

    What device and platform are you using? 

    Are you seeing an issue with your clock period?

  • 0 in reply to David Friedland
    Intellectual 670 points

    I'm just wondering where the PLL and clocking is set up. Does the SYS/BIOS do any of this setup or is it the GEL file that shall do that?

     

  • 0 in reply to Marko S
    TI__Mastermind 18320 points

    Again, what device and platform are you using? 

  • 0 in reply to David Friedland
    Intellectual 670 points

    It is a C6748 on a OMAP-L138 EVM.

     

  • 0 in reply to Marko S
    TI__Mastermind 45025 points

    Hi Marko Siponen,

    The platform sets a default CPU speed.  For OMAPL138 this is set to 300MHz.  You can view and/or edit the platform using the RTSC platform wizard (see this link for details on the platform wizard: http://rtsc.eclipse.org/docs-tip/Demo_of_the_RTSC_Platform_Wizard_in_CCSv4)

    The GEL files also allows you to change this using different PLL multipliers and dividers.  For example, the OMAPL138 GEL script that I have has a function:

    Set_Core_300MHz() {
        device_PLL0(0,24,1,0,1,11,5);
        GEL_TextOut("\tPLL0 init done for Core:300MHz, EMIF:25MHz\n","Output",1,1,1);
    }

    I've attached the GEL file so you can see more details on the above code if you like.

    Steve

    1754.omAPL138_DSP.txt

  • 0 in reply to Steven Connell
    Intellectual 670 points

    Hello again

    I have now moved my code to a custom board. The board uses a 25MHz oscillator. On the evaluation board it was 24MHz.

    I have made the changes in the GEL script to run at 300MHz. But how do I tell SYS/BIOS what frequency the oscillator has? I can’t find a setting for it.

    If I debug my code in CCS4 I can see in the register view that TIMER64P0DSP->TIM12 is set to 24000. Shouldn’t it be 25000 to get a 1ms timer?

    And one more question. I would need to use the Timer0 to drive pin TPM64P0_OUT12. Is this possible or do we have to re-CAD the board?

     

  • 0 in reply to Marko S
    Intellectual 670 points

    I found some settings under Target Specific Support:

    I have seen that this changes the TIMER64P0DSP->TIM12. Is this the correct place to change this?

    And one more question. Why does it say C64P and not C67P under Target Specific Support. I use a C6748, so I have selected a "Generic C674P Device":

  • 0 in reply to Marko S
    Intellectual 670 points

    Now I have tested more things. I found a way to select which timer to use for systick:

     

    This enables me to use timer3. :-)

    But now I have one more question (again). I see that this change make SYS/BIOS use CPUINT7 instead of CPUINT14. What defines which CPUINT is used?

     

     

  • 0 in reply to Marko S
    TI__Mastermind 20805 points

    Marko --

    Unfortunately, there's no way to specify which interrupt id for the Clock module to use for the timer.  This information cannot currently be passed down thru our hal.Timer interface.

    There is a workaround.

    [1]  update the Clock module to specify that the application call Clock_tick() by adding the following to your .cfg file:

    var Clock = xdc.useModule('ti.sysbios.knl.Clock);
    Clock.tickSource = Clock.TickSource_USER;

    [2]  create a timer object that uses timer 3 and have it call an ISR that calls Clock_tick().  Add the following to your .cfg:

    var timer0Params = new Timer.Params();
    timer0Params.instance.name = "myTimer3";
    timer0Params.period = 1000;
    timer0Params.intNum = 14;
    Program.global.myTimer3 = Timer.create(3, "&myTimer3isr", timer0Params);

    [3]  Add the myTimer3isr() C function to your app.c:

    Void myTimer3isr()
    {
        Clock_tick();
    }

    I verified that this works on my 6748 setup and I've attached a CCSv5.1 project.  You can extract the .c and .cfg and create a project of your own if you are using CCSv4.2.

    7433.task6748.zip

    Regards,
    -Karl-

     

    P.S.  This thread was marked answered.  It would be good to open a new thread for the next issue so that it shows up as a new issue.  Threads that are marked answered don't get as much attention as threads that are still open.  But, we can continue to work this issue on this thread.

     

  • 0 in reply to Karl Wechsler
    Intellectual 670 points

    Thank you for your reply. I will follow your suggestion.

    And how about the C64P under the under Target Specific Support. Why does it say C64P and not C67P?

     

  • 0 in reply to Marko S
    TI__Mastermind 20805 points

    The 67P is the 672x device which is much different than the 674x.

    The 674x is really just a 64x+ (64P) with floating point.   So, some of the support modules to support 674x are identical to the 64x+ and we therefore use 64P for them.   If you go to cdoc in the family package, you should see a "Delegates" link and you can see the delegates for your given target.

    -Karl-