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TMS320C6678: HyperLink MPY factor Selecting problem

user4855311
Prodigy 20 points
Part Number: TMS320C6678

Dear Sirs,

I have a problem from HyperLink MPY factor selection.

In datasheet page, I know that I can use the equation to choose the desire MPY factor.

PLL_OUTPUT=REFCLK*MPY

And the MPY magnification value need to setting between 4x-25x in datasheet page,as : 

 

PLL multiply. Selects PLL multiply factors between 4 and 25.

00010000b = 4x

00010100b = 5x

00110000b = 6x

00100000b = 8x

00101000b = 10x

00110000b = 12x

00110010b = 12.5x

00111100b = 15x

00111100b = 16x

01000001b = 16.5x

01010000b = 20x

01011000b = 22x

01100100b = 25x

I want to know the relation and regulation between MPY register setting value and the magnification value.

And why when set magnification=15x & 16x, the MPY has the same register value? 

Best Regards,

Yvonne.lu

  • 0
    TI__Guru 65405 points
    The team is notified. They will post their feedback directly here.

    BR
    Tsvetolin Shulev
  • 0 in reply to Cvetolin Shulev-XID
    TI__Guru* 95265 points
    Hi,

    That is a typo. For typical usage, you can select the MPY based on the Table 2-6 Example Operating Rate Configurations of the Hyperlink user guide, 16x should be 01000000b.

    Regards, Eric
  • 0 in reply to lding
    Prodigy 20 points

    Hi Iding,

    The Example Operating Rate Table is another problem~

    If I use RefClk=312.5MHz  MPY=5 Output PLL= 1.5625GHz , at this table means I can't use the Quarter and Eighth RateScale ?

    Because I saw that some blocks typed 'x'.

    If I want to adjust MPY to multiply Output PLL=1.5625GHz (RefClk=312.5MHz ) to 5.3125GHz, at Table3-31 mean I can't choose the 17x MPY ?

    But Table 3-31 tells that PLL MPY could selet between 4 and 25.

    Best Regards,

    Yvonne.lu

  • 0 in reply to user4855311
    TI__Guru* 95265 points
    Hi,

    The input clock can be:
    156.25 Mhz
    • 250 MHz
    • 312 MHz

    PLL_OUTPUT=REFCLK*MPY
    The MPY field can be programmed to several values; however, the PLL_OUTPUT
    value must be in the 1.5625 GHz to 3.125 GHz range.

    The Hyperlink typical runs for 3.125G, 6.25G and 10G. Please let me know what is your intended baud rate for Hyperlink?

    If I use RefClk=312.5MHz MPY=5 Output PLL= 1.5625GHz , at this table means I can't use the Quarter and Eighth RateScale ? =====> running at that low speed is meaningless for such a high speed interface.

    If I want to adjust MPY to multiply Output PLL=1.5625GHz (RefClk=312.5MHz ) to 5.3125GHz, =====>PLL_OUTPUT
    value must be in the 1.5625 GHz to 3.125 GHz range.

    Point is typical customer runs at 3.125G, 6.25G and 10G., you can select the MPY based on your input clock to get that speed.
    Due to Silicon errata, Advisory 21 HyperLink Data Rate Limited to 40 Gbaud Issue, you can't run 12.5G.

    Regards, Eric