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TMS320C6678: unit of "c2t_delay = 0" in "nysh.spi.map" of C6678

Kanae
Mastermind 9655 points
Part Number: TMS320C6678

Hi, Keystone Support Team,

I would like to know the unit of "c2t_delay = 0" in "nysh.spi.map" of C6678.
Is it "nano seconds" or "clocks"?
My customer would like to set "c2t_delay" to "5 nano seconds".
Could you please inform how to set properly "c2t_delay" in "nysh.spi.map" of C6678?

Best regards,
Kanae

  • 0
    TI__Guru 65405 points
    I've forwarded your query to the software experts. Their feedback should be posted here.

    BR
    Tsvetolin Shulev
  • 0
    TI__Guru** 114410 points
    c2t delay is interms of SPI clock cycles. It maps to C2T delay described in the SPIDELAY register in the SPI USer guide:
    www.ti.com/.../sprugp2a.pdf
  • 0 in reply to Rahul Prabhu
    Mastermind 9655 points

    Hi Rahul,
    Thank you for your reply.
    Is c2t delay in "nysh.spi.map" SPI clock cycles?

    If my customer sets "c2t_delay = 5 " in "nysh.spi.map" at SPICLK=666kHz,
    tC2TDELAY is 7.5 micro sec.

    Or

    "c2t_delay = 5 " in "nysh.spi.map" means the C2TDELAY field value in SPI Delay Register.
    If so, I checked the example fomula in the user guide; Page-3-14.
    ***********************************************
    The setup time value is calculated as follows:
    tC2TDELAY = (C2TDELAY + 2) × SPI module clock period
    Example:
    SPI module clock = 25 MHz -> SPI module clock period = 40 ns;
    C2TDELAY = 06h; then tC2TDELAY = 320 ns;
    ***********************************************

    If my customer sets "c2t_delay = 5 " in "nysh.spi.map" at SPICLK=666kHz,
    tC2TDELAY = (5 + 2) × 1.5 (SPI module clock period)=10.5　micro sec.

    Which understanding is correct?

    Best regards,
    Kanae

  • 0 in reply to Kanae
    TI__Guru** 114410 points

    Sorry for the delayed response. for reference we provide the ROM bootloader source here:

    processors.wiki.ti.com/.../Keystone_Device_Architecture

    Here is the trace of the setting in the BootROM:

    spiCfg.c2tdelay  = p_boot_params->c2tdelay;   //configuration copied from boot parameter table.

       ret = hwSpiConfig (&spiCfg);

                  SPI_REG_SPIDELAY_SET_C2T(v, cfg->c2tdelay);

                            #define SPI_REG_SPIDELAY_SET_C2T(v, delay)    (v) = BOOT_SET_BITFIELD((v), delay, 31, 24)

    So it appears the value in the boot parameter table is used to set the field which means it corresponds to your second option.

    Regards,

    Rahul