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Routing video paths

Xavier Tisaire
Intellectual 310 points

Hi all,

 

I'm trying to route a board for the dm6467t, and I've got a question, actually I want to play video at the same time with many IC, so i'd like to send the same information from the VPIF port to different IC at the same time. The question is: Can i just short circuit the buses or is there any other option much more elegant?

 

Regards,

Xavi

 

  • 0
    TI__Mastermind 43875 points

    Xavi,

    If the formats for the various output destinations are the same then you can simply connect the data to the multiple destination ICs as long as you do not violate the capacitive loading of the DM outputs.

    Check the data sheets for the DM (to determine the max load) and the target ICs (to check their input load capacitances) to make sure there isn't too much load for the frequency you are trying to drive.

    BR,

    Steve

  • 0
    TI__Intellectual 785 points

    Xavi,

     

     For the data lines, you can get away with tying them all together as long as you understand the interface timing implications of the particular routing topology you use.You need to be careful with the clock, though. If you're only going two places, you can get away with splitting the line near the clock source and providing serial termination on each leg of the clock. The two branches should be matched in length. If you're going more places than that, I recommend a fanout buffer - you might need a zero-delay buffer depending on how much timing margin these interfaces have.

     

    The more elegant and safer option is to use buffers to assist in fanout on all signals. These can be use with our without registers depending on the interface timing needs.

  • 0 in reply to ToddHiers
    Intellectual 310 points

     thanks a lot, I'll try it without buffers then, seems like the previous mux can afford it. By th way, whe you say serial termination do you mean terminating it with a matched impedance?

     

    Regards,

     

    Xavi

  • 0 in reply to Xavier Tisaire
    TI__Intellectual 785 points

    > By the way, when you say serial termination do you mean terminating it with a matched impedance?

    Yes. In practice exact matched impedance is not necessary (or practical), but some resistance is needed to keep the source impedance close enough to the transmission line impedance for good enough signal integrity. Something in the 10-33 Ohms range typically works fine.