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CDCE62005: How to manage programming when used with TMS320C6678

Larry Shaffer
Prodigy 240 points
Part Number: CDCE62005
Other Parts Discussed in Thread: TMS320C6678, LMK03318, CDCE6214

Hello,

Since we are starting a new design with the TMS320C6678, I understand that the CDCE62005 is a good choice to provide the LVDS clocking for the DSP: 100MHz for the core, 50MHz for the DDR, and 250MHz for the SGMII. Please let me know if that is my best choice first of all. Assuming that is reasonable, what I'm trying to figure out is the programming. Of course I plan to connect the SPI interface of the DSP to the CDCE62005. My second question is after I have worked out how to program the registers in the CDCE62005, how would the factory program the CDCE62005 before they solder it onto the board? My third question is that if we have a problem with our prototype boards such that the DSP is not running well enough to reprogram the CDCE62005, is there a way to re-program the CDCE62005 in-system?, maybe by connecting a header to the SPI pins and using some kind of programming cable/adapter from a PC?

  • 0
    TI__Mastermind 28540 points
    Larry Shaffer said:
    Since we are starting a new design with the TMS320C6678, I understand that the CDCE62005 is a good choice to provide the LVDS clocking for the DSP: 100MHz for the core, 50MHz for the DDR, and 250MHz for the SGMII. Please let me know if that is my best choice first of all. Assuming that is reasonable

    Something to be aware of that we just released is the clock tree architect, webench.ti.com/clock-tree-architect, for finding clocking solutions.

    The CDCE6214 or LMK03318 may also be a good choice for you.  As for best choice what are your metrics?  The CDCE62005 may also be reasonable for you.

    Larry Shaffer said:
    My second question is after I have worked out how to program the registers in the CDCE62005, how would the factory program the CDCE62005 before they solder it onto the board?

    At this time we don't offer a factory side programming. However I might suggest that after you soldered on to program it in-system during production testing. Do require pre programmed devices before soldering to the board?  It appears you're hoping for a clock for your DSP on first power up?

    The LMK03318 default EEPROM does support 100 MHz output.

    Larry Shaffer said:
    My third question is that if we have a problem with our prototype boards such that the DSP is not running well enough to reprogram the CDCE62005, is there a way to re-program the CDCE62005 in-system?, maybe by connecting a header to the SPI pins and using some kind of programming cable/adapter from a PC?

    The CDCE62005 can be reprogrammed in system, as is the case with the other devices.

    73,
    Timothy

  • 0
    Prodigy 240 points

    Hi Timothy,

    Thanks for the suggestions. I tried out the clock tree architect tool. My metrics are first of all to meet the jitter specs and the other requirements needed by the TMS320C6678, second priority is power consumption, third would be board space, and lastly price. And as mentioned earlier ease of device programming is important. 

    Our board design is very dense so we do not have a bed-of-nails in-circuit test capability. We would somehow need to pre-program the CDCE62005 before it was soldered down to the board. We would like pre-programmed devices somehow.

    Yes - I am hoping for a clock for my DSP on first power-up. There are not any other devices on the board such as a FPGA or another processor that could program the CDCE62005 on behalf of the DSP.

    Could any of the programmer tools such as Data I/O or BP Microsystems maybe work for us?

  • 0 in reply to Larry Shaffer
    TI__Mastermind 28540 points

    Hello Larry,

    Looking quickly at the performance specifications in the DSP datasheet.  I see 4 ps, 8 ps, and 0.02*tc(CORECLK) max peak-to-peak.   I think 0.02*tc(CORECLK) = 0.02 * (1/100 MHz) = 200 ps.  When dealing with peak to peak noise specifications, we convert to RMS given a probability based on a bit error rate.  BER 1:10^12 is a factor of 14, BER 1:10^15 is a factor of 15.9.   4 ps p-p / 15.9 = 250 fs rms.  LMK03318 can meet that specification.

    It appears that the programmer tools would work.  I noticed that BP Microsystems supports the LMK03318.

    Of course with the LMK03318 default EEPROM supporting the frequency of 100 MHz AC-LVPECL output, which is a clock having amplitude of Vod = 800 mV == Vdiff = 1600 mVpp, using the default EEPROM --- if the DSP can program the LMK03318 - then the DSP could update the EEPROM to final values.

    You could also boot in ROM mode, LMK03318 has 64 pages of ROM codes.  ROM code 45/46 provide 250 MHz, 100 MHz, but not 50.  You can always update the programming after start-up from the DSP.

    I think the LMK03318 is a good option for you.

    73,
    Timothy

  • 0 in reply to Timothy T
    Prodigy 240 points

    Thanks for your help and suggestions Timothy,

    I'll look at the LMK03318. That's pretty neat that is has a bunch of options already programmed in ROM.

    Larry