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rtos tiva BIOS clear FPU registers

Zaraki
Prodigy 70 points

Hey,
Bios 6.4 TiRTOS 2.02.36 CCS6

1. Main: 

    // ....Set FPU
    FPULazyStackingEnable();
    FPUEnable();

    /* *** *** START BIOSU	 *** *** */

    //System_printf("exit main()\n");
    //Breakpoint One
    BIOS_start();    /* does not return */
    return(0);
}

2. FPCC = 0xC0000000

3. The problem is that after BIOS start, FPCC=0x0000000 .And FPU does not work properly - sometimes are calculating errors.


4. When i add lines AFTER BIOS started:
FPUEnable();
FPULazyStackingEnable();

FPU works properly and calculations are good.

So question: Is is normal that BIOS clear fpu config? Can i call FPULazyStackingEnable() after bios started?




  • 0
    TI__Mastermind 45025 points

    Hi Zaraki,

    I saw it mentioned another thread that the FPU is enabled by default (although I cannot confirm that this is true).

    Zaraki said:

    4. When i add lines AFTER BIOS started:
    FPUEnable();
    FPULazyStackingEnable();

    FPU works properly and calculations are good.

    Since BIOS_start() doesn't return, I don't think those FPU functions are even being run.

    Zaraki said:
    PU works properly and calculations are good.

    What happens if you don't call these two FPU functions (comment them out or delete them).  Does this observation still hold true (i.e. is it still working properly?).  If yes, then that would imply that it's indeed enabled by default.

    Steve

  • 0 in reply to Steven Connell
    Prodigy 70 points

    BIOS clear stacking configuratiotion because it is not support by SYS/BIOS. If i call FPU(Lazy)StackingEnable() bios will crash.

  • 0 in reply to Zaraki
    TI__Mastermind 45025 points

    Zaraki,

    Which TivaWare are you using?  Is it the TivaWare that ships with TIRTOS? Or did you install TivaWare separately (from TivaWare download site, for example)?

    Zaraki said:
    BIOS clear stacking configuratiotion because it is not support by SYS/BIOS. If i call FPU(Lazy)StackingEnable() bios will crash.

    Can you please clarify on this?  I'm just curious how you came to this conclusion.  Was this stated in some documentation somewhere?

    Zaraki said:
    If i call FPU(Lazy)StackingEnable() bios will crash.

    Again, can you please provide further details?

    Steve

  • 0 in reply to Steven Connell
    Prodigy 70 points

    I am using TivaWare that ships with TITROS.

    Tere isn't any documentation about it. It is my own conclusions. Maybe i am wrong.

    Just simple project with one Task after calling one of these functions crash.