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how to use "delete cell" or any block syntax to let Assura ignore bit cell?

lijulia

We used faraday memory compiler to generate memory cell .gds file and stream in to the Cadence, but got Assura LVS errors when we did chip  top level lvs check,and most issues related to the dummy cells in the memory block, eg. SHLD_DMY_CORNER_SE cell;

 And we got this reply from the faraday "Since the bit cell using special design rule.  It is not a standard logic device. your error is caused by Assura LVS command file. As you know , our memory was pass CALIBRE DRC/LVS ,and has good yield in silicon. Our suggestion is not to check the bit cell by using Assura DRC/LVS.The memory bit cell was provided by foundry , UMC and Faraday will insure the bit cell was correct. Please ignore all bit cell error when you running DRC/LVS (maybe use "delete cell" or any block syntax to let Assura ignore bit cell) "

 

But I already tried ignore cells, blackbox etc.; but nothing work; after I flatten the whole top, it didn't complain the pin mismatch of the dummy cells but got other errors...

 

Please give me some suggestion about this, thanks

 

 


Parents

  • Hi Julia

    If you use ?ignoreCell cmd from avParameters section, you will ignore the cell for layout extraction. If you would like to include the cell in lvs database for subsequent parasitic extraction using QRC but want to ignore it for comparison, then you can use ignoreCell from avCompareRules. E.g.

    avCompareRules(
       schematic( ignoreCell( cell("myBitCell") ) )
       layout( ignoreCell( cell("myBitCell") ) )
    )

    The above cmd ignores the bit cell in both schematic and layout.

    Unless it is for a very simple cell, it is never an easy process to match the lvs results of a tool to that of another tool. This is due to the different rules used by both tools (e.g. different ways of identifying pins, etc). An easy way for you to duplicate Calibre results is to simply use PVS instead of Assura. PVS can read in Calibre rules as it is.

    You can try the following Assura cmds:
    a. Use pinTextFile to add top level pins to resolve the pin mismatches. But look at the erc file first to check if there are any reasons why existing pins (if any) are not captured. Perhaps it is simply due to some typo in textToPin cmds in the extract rules file.

    b. Use expandOnError cmd to automatically promote cells if there are pin, device count, parameter, etc mismatches.

    c. Check for possible missing cell bindings and add bind cmds if necessary.

    d. My preference is to always start with "device" errors because most of the time, resolving the device errors would also resolve the net errors.

    Best regards
    Quek

Reply

  • Hi Julia

    If you use ?ignoreCell cmd from avParameters section, you will ignore the cell for layout extraction. If you would like to include the cell in lvs database for subsequent parasitic extraction using QRC but want to ignore it for comparison, then you can use ignoreCell from avCompareRules. E.g.

    avCompareRules(
       schematic( ignoreCell( cell("myBitCell") ) )
       layout( ignoreCell( cell("myBitCell") ) )
    )

    The above cmd ignores the bit cell in both schematic and layout.

    Unless it is for a very simple cell, it is never an easy process to match the lvs results of a tool to that of another tool. This is due to the different rules used by both tools (e.g. different ways of identifying pins, etc). An easy way for you to duplicate Calibre results is to simply use PVS instead of Assura. PVS can read in Calibre rules as it is.

    You can try the following Assura cmds:
    a. Use pinTextFile to add top level pins to resolve the pin mismatches. But look at the erc file first to check if there are any reasons why existing pins (if any) are not captured. Perhaps it is simply due to some typo in textToPin cmds in the extract rules file.

    b. Use expandOnError cmd to automatically promote cells if there are pin, device count, parameter, etc mismatches.

    c. Check for possible missing cell bindings and add bind cmds if necessary.

    d. My preference is to always start with "device" errors because most of the time, resolving the device errors would also resolve the net errors.

    Best regards
    Quek

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