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check_dft question -help

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bradyue

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When I am doing check_dft, some warnings were reported:
Warning: Cell I_RF1R1W16X288/RF1R1W16X288 (RF1R1W16X288) is unknown (black box) because functionality for output pin FFO[287] is bad or incomplete. (TEST-451)

When I check the RTL, I found all the RAM model has that issue.

When I refer to the library, I didn't find anything wrong.

Who can answer me... thanks
 

Hi,

Test compiler requires that you have a functional model in your library for each leaf cell in your design. Test compiler uses the functional model to perform test pattern generation. If you use cells that don't have a functional models, TC displays the warning you mentioned. So just check the RAM models.

Rgds,
CSuresh
 

I am so appreciated about your kindly reply..

so, it seems that warning could be omitted.
 

Hi,

Try to remove all the warnings. Since, Test compiler doesn't know the functional behavior of a missing cell, so it can't predict the o/p of missing cell resulting in low fault coverage.

Suresh
 

Hi,

First thing I you are using a very old flow "check_dft". The new command is dft_drc and it has an all together different flow. You have to create protocol etc...

Now for this error, you can do nothing for this in DFT Compiler and you can just ignore them.

But in Tetramax ,if you have a low test coverage and you plan to do fast sequential ATPG then it will be beneficial to have the simulation model of these memories. If not then as Suresh has mentioned the output of these Memories are going to be "X". This will effect both your coverage and compression ( If implemented).

-cheers
vlsi_eda_guy
 

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