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AM1808 IBIS File (Missing model informations on DDR2 model section)

bluecad
Prodigy 20 points
Other Parts Discussed in Thread: AM1808, OMAPL138

Hi,

 IBIS model of AM1808 or OmapL138 processor does not have  adequate information for DDR2 simulation.

Because : In IBIS file contains BSSTL18TCSCGPBFZ Model selector and it consist of only Fast Mode of NOSR0_NOTERM_1P8 (%10 variation) and

NOSR0_NOTERM_0.1_1P8 (100mV variation). I did not understand why it is FAST, what the mean of FAST? Which model does it correspond to in page 46

of DDR2/mDDR user guide.

This page shows that 2 drive strentgth (Normal and Weak) of DDR2 and

4 drive strength (Full, 1/2, 1/4 and 3/4) of mDDR. These drive strength should be contained  in the model selection of IBIS model like other microprocessor IBIS model.

This is not a case for DDR2 ICs. Because of its IBIS model contains FULL and HALF model.  

I wonder any users of AM1808 does not need to IBIS model, or TI did not noticed so far (!!!). (For example LogicPD or Spectrum Digital , does not use IBIS model for signal integrity simulation on own board? It is so interesting. Because of datasheet contains generic placement and constraints.

Thanks for your answers.

Best Regards,

FERHAT YALDIZ

 

  • 0
    TI__Mastermind 27585 points

    Ferhat,

    The drive strength settings only apply to the DDR2/mDDR devices. You will find different models for each mode in the memory IBIS models, not the controller.

    The Fast Mode corresponds to the slew rate of the output buffers. This is not a user configurable setting, so it is not in the user guide.

    As for the datasheet routing rules, they completely specify the routing of the interface and apply to every DDR2/mDDR design. They are part of the controller timing specification and should be treated as such.

    Jeff