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TMS320F280041C: SDFM (Sigma Delta Filter Module) Pin Config..

Part Number: TMS320F280041C
Other Parts Discussed in Thread: AMC1210

Hi Team C2000,

WRT the TMS320F280041C SDFM.. when running in mode=2, the TRM (last section of page 1690 (SPRUI33d ) states..

"When MOD=2, data and modulated clock signals are encoded into modulated data as shown in Mode 2 of Figure 17-4. In this mode, the clock input SD-Cx pin should be left floating. The input control unit performs continuous automatic calibration to achieve optimum decoding performance."

Customer asks.. "Must this (SD_Cx) pin physically be left floating or can I just use this pin for a different purpose?"

Thanks, Merril

  • Merril,

    We recommend to avoid mode2 (manchester mode) for newer application. We strongly recommend using mode0 as it provides best noise immunity when your synchronize GPIOs with respect to SYSCLK. Please check advisory

    Advisory: Advisory SDFM: Manchester Mode (Mode 2) Does Not Produce Correct Filter Results Under
    Several Conditions

    Regards,

    Manoj

  • Hi Manoj,

    Thx.  Yes, I saw that in the errata.  How strong is "recommend" to not use it? 

    If customer chooses to use it anyway, what is the answer to my prior question? 

    If SDFM won't work on this device.. which device do you recommend as the nearest replacement/substitute device?

    Thanks, Merril

  • Merril,

    Thx.  Yes, I saw that in the errata.  How strong is "recommend" to not use it? 

    We don't want customer to use mode2 in their new design as mode2 is extremely vulnerable to noise glitches, dutycycle jitter, frequency jitter can cause incorrect (unpredictable) filter output. So, please refrain from using it.

    If customer chooses to use it anyway, what is the answer to my prior question? 

    Unused pins in SDFM mode 2 can be used as regular GPIO (or) other peripheral pin. You don't need to leave it floating.

    If SDFM won't work on this device.. which device do you recommend as the nearest replacement/substitute device?

    SDFM works. It is just that we want customer to use Mode 0 and not Mode 2. If want to use Mode2 only. Then consider using AMC1210 (which supports Mode 2) and then interface with F280041C using SPI.

    Regards,

    Manoj