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Re: DM365 Hardware questions

Doug Goss
Intellectual 290 points

Tai,

Thanks for the response. On question #2, for clarification ..

We need to conserve board space so we don't want to use two jtag connectors. The two DM365's will be relatively close together.

Reading the info in the Wiki, it appears that what i need to do is to loop the TDI thru the TDO and the TCK thru the RTCK. Is that correct?

What is the safe distance, before i need to worry about using buffers?

Thanks,
Doug

  • TI__Guru**** 171044 points

    Doug,

    Apparently your reply lost track of its original thread. I will move to the correct forum and add pointers to both threads.

    Original thread: http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/100/p/53227/188624.aspx

    Cheers,

    Rafael

  • in reply to desouza
    TI__Expert 8055 points

    Doug,

    I think you can find some useful information at the following location http://processors.wiki.ti.com/index.php/XDS_Target_Connection_Guide

    The safe distance for the JTAG traces without using buffers is 6 inches (total scan chain length).   

    And regarding "Reading the info in the Wiki, it appears that what i need to do is to loop the TDI thru the TDO and the TCK thru the RTCK. Is that correct?", it's partially correct. The TDO if the =1st device is connected to the TDI of the 2nd device, and so on, in a daisy chain.  But the TCK/RTCK are not routed in series like that.  They are connected in parallel.  But take note of the following article on adaptive clocking.

    http://processors.wiki.ti.com/index.php/XDS_Target_Connection_Guide#Multi-device_Adaptive_Clocking

     

    Regards,
    Dan

     

  • in reply to DanRinkes
    Intellectual 290 points

    Dan,

    I looked at that info and that is where my confusion came from.

    If you look at Figure 3, it agrees with what you are saying about RTCK. However, it appears that it is only hooked up this way because the target device, in this case, does not support RTCK. The DM365 does.

    Therefore, it should be hooked up as shown in Fig 5, with RTCK/TCK in a chain, just as TDI/TDO are.

    What am i missing?

    Thanks,

    Doug

  • in reply to Doug Goss
    Intellectual 290 points

    Sorry to be a pest, but can somebody please confirm if i am reading the wiki correctly or if Dan is right.

    I need to finish this design.

    Thanks,

    Doug

  • in reply to Doug Goss
    TI__Prodigy 390 points

    Since you have two Identical devices which both support RTCK, use figure 5, which cascades RTCK from 1st device to TCK of second device. 

    You must use an adaptive clocking emulator or guarantee the input TCK freq NEVER exceeds the output RTCK frequency or the devices will loose sync.

     

    Lee