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OMAP-L137 series terminations and pullups on MIFB

Ted Michon
Prodigy 230 points
Other Parts Discussed in Thread: OMAP-L137

The Spectrum Digital EVM module for the OMAP-L137 seems to put 22 ohm series termination resistors on every line. On the EMIFB interface, for eample, they are on the address, CAS, WE, RAS, CAS and data. Series termination works when placed at the source end of a signal, so it's fine for address, CS, RAS, and CAS, but how does this help with data, which can be sourced at either end of the line?

Where are termination requirements and guidelines for the L137 covered? There's nothing in the EMIFB user guide or the L137 Reference Guide.

Also, the EVM has 10 K pullups on teh EMIFB DQMs, RAS, CAS, Clk, CS, and SDCkEn. What's going on here and is this covered somewhere in the docs?

-Ted

  • 0
    TI__Mastermind 24340 points

     

    Currently there are no layout guidelines for this device other than the EVM. We recommend you follow what was done on the EVM and include the series terminators on the EMIFB interface. The pullups on the EMIFB control signals, however, are not necessary. As for the placement of the resistors on the data lines, they should go near the strongest buffers, which will be on the external memory devices.  Also, for series termination, the clock, strobes, and data lines are most important. The address and control lines are not as critical.