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TMS320F280049C: Loading Program for Flash vs RAM

Qasim Zia0
Prodigy 20 points
Part Number: TMS320F280049C

Hi, I am generating a sine wave using DACA of a certain frequency. Sine table consists of 10 samples. I am a little bit confused that when I program the code in flash i get a different frequency at output and when I program the same code in RAM I should get the same frequency because the code is same, instead, I get a different frequency for the same code. Please guide me why is this happening.

  • 0
    TI__Guru* 87105 points
    Qasim,

    Please note that RAM is 0-wait stated memory where as Flash accesses incur few wait-states - this can be the reason.

    Please see Table 5.9.4 Flash Parameters in datasheet www.ti.com/.../tms320f280049.pdf.

    Hope you configured the wait-states correctly (RWAIT bit field in FRDCNTL Register) as per the operating frequency. Please check.

    Make sure you enable prefetch (FRD_INTF_CTRL). This helps to balance the delay from wait-states for linear code.

    Thanks and regards,
    Vamsi
  • 0 in reply to Vamsi Gudivada
    Prodigy 20 points

    I would check into these. But as the frequency of the sine wave is the function of delay between two samples. Now the delay remains and I have confirmed it from the oscilloscope that if the timer is configured for 2us then it exactly triggers after 2us for both cases.

    This is the pseudo code

    while(1)
{ 

while(!timerFlag);\\let say that timer rises an interrupts each 2us
setDACshadowvalue

}

  • 0 in reply to Qasim Zia0
    TI__Guru* 87105 points

    Qasim,

    Ok, please check and let us know if you have further questions.

    As you know, you can execute ISR from RAM as needed.

    Thanks and regards,
    Vamsi