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TMS320F28335: Problem in SCI Baud rate Setting

Seelam Prabhu
Prodigy 70 points

Part Number: TMS320F28335

Hi,

I am working on SCI UART Comm...

I fully didn't understand the Baud rate setting... Please help me to understand it.

Here:

#define CPU_FREQ 150E6
#define LSPCLK_FREQ CPU_FREQ/4
#define SCI_FREQ 100E3
#define SCI_PRD (LSPCLK_FREQ/(SCI_FREQ*8))-1

SciaRegs.SCIHBAUD = 0x0000;
SciaRegs.SCILBAUD = SCI_PRD;

So Now what is the Baud rate?

If I calculate SCI_PRD value = 45.87500

How did it set to Baud rate?

Many Thanks,

  • 0
    TI__Mastermind 26850 points

    Hello Seelam,

    The baud rate is calculated as follows,

    Ideal Baud = LSPCLK/(BRR+1)*8

    So in order to find what BRR is (value to write to baud rate register), we can rearrange the equation to be,

    BRR = (LSPCLK/(Ideal Baud*8))-1 

    Which from the defines above, BRR is SCI_PRD. 

    You are right, SCI_PRD is 45.87. The value that will be written to the baud rate register is 45, so if we do the calculation again,

    Baud Rate = 60M / ((45+1)*8) = ~101902

    Doing a BRR value of 46 actually gets you closer to 100k,

    Baud Rate = 60M / ((46+1)*8) = ~99734

    Best Regards,

    Marlyn