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convertion multi striped devices to multiple instances

dwaraka

 I have mosfets and resistors placed as multi striped devices in schematic. I want to convert it to mulple instances.

for example

if the schematic has a nmos with width 100u and 10 stripes, I want it to be changed as 10 different instaces of 10u width connected in parallel.

And if there is a resistor with length 50u of 5 stripes, after the conversion it should have 5 resistors, each of length 10u length, connected in series.

Could any one please help me in writing a skill script for this.

Thanks

 

  • Andrew Beckett

    Why? What do you mean by "stripe" (is that a parameter of the device?). If this is for layout purposes, layout XL can already split single devices into multiple devices based on an m factor (which can be any parameter you like). Splitting into separate devices is a good way of slowing down simulation, so knowing why you want to do this is important - you may be shooting yourself in the foot unless you have a very good reason for doing this.

    Andrew.

  • dwaraka
    Hello Andrew,

    Stripe means finger of the device. (For example, If a mosfet has 100um width, we can devide this to multiple fingers whose width adds up to 100)

    The purpose is to make sure that the number of fingers in layout and schematics are same. If we are starting the layout from scratch, we can make use of all these features of XL etc. For a design which is already been laid out, if I need to check the correctness of number of fingers, there is no way with the verification tool (Hercules) we are using. We can overcome the limitation of the tool if it gets a netlist with multi fingered device netlisted as multiple devices. In this case if I specify not to merge the parallel mos or series resistors, the tool look for the schematic equivalent for each stripes of layout devices. Otherwise when it merge parallel or series devices it will have only the info of total size of the device, will not have any information of number of fingers. I am not going to use this netlist for any simulation, it is just for the lvs verification.

    Please let me know if you need any more info.

    Thanks,
    Vijith
  • Andrew Beckett

    Vijith,

    I suspect there is a way of doing this with Hercules, given that there is a way of doing it with Diva and Assura (and I suspect PVS, although I've not checked) by ensuring you have comparison rules that look at the "stripe" parameter as well as w and l. If you really do have to modify the schematic, something along these lines should help (I just wrote this and it has had very limited testing):

     

    procedure(CCFconvertParamToIterated(cvId paramName)
  let((newName width m paramType)
    foreach(inst cvId~>instances
      m=dbGet(inst paramName)
      paramType=type(m)
      when(stringp(m) m=atoi(m))
      when(m && m!=1
        ;----------------------------------------------------------------
        ; Come up with new instance name
        ;----------------------------------------------------------------
        width=dbGetNameNumBit(inst~>name)
        rexCompile("[<:>]")
        sprintf(newName "%s<%d:0>"
          rexReplace(inst~>name "__" 0)
          width*m-1
        )
        if(stringp(paramType) then
          dbSet(inst "1" paramName)
        else
          dbSet(inst 1 paramName)
        )
        inst~>name=newName
        ; might need a call to CCSinvokeInstCdfCallbacks at this
        ; point to call callbacks if necessary.
        ; Solution 11018344 on http://support.cadence.com contains the code
      )
    )
    schCheck(cvId)
  )
)

     


    You'd call CCFconvertParamToIterated(geGetEditCellView() "m")

    or whatever the parameter is called. Hopefully it's clear enough that you can adapt it to meet your needs.

    Andrew.

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