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Modifying Pcells from PDK

nosaj

Hi all,

 I'm looking for ways to slightly modify Pcells (transistors, res, etc) from a PDK. 

I've come across two db functions :

DumpPcDefinePcell and WriteSkill

The idea is to dump the skill code from the Pcell, modify the code and recompile it. But the files that these fuctions return are not exactly easy to read. And some even contains callbacks from the PDK that most likely is encrypted.

example :

dbD_0xf1156512 = dbCreateRect(dbD_0xf1156612 list(236 -1)
        list(-1.100000e-01:0.000000e+00 1.500000e-01:1.200000e-01))
dbD_0xf1156513 = dbCreateRect(dbD_0xf1156612 list(75 -1)
        list(-2.700000e-01:-1.600000e-01 3.100000e-01:2.800000e-01))
dbD_0xf1156516 = dbCreateRect(dbD_0xf1156612 list(26 -1)
        list(-2.400000e-01:-2.000000e-01 2.800000e-01:3.200000e-01))
dbD_0xf1156515 = dbCreateRect(dbD_0xf1156612 list(26 -1)
        list(-2.900000e-01:-2.000000e-01 -2.400000e-01:3.200000e-01))

Is this the actual code the foundry used to compile the Pcell or is it something that's Virtuoso spills out based on the compiled Pcell?

How should one go about modifying the Pcell layout from these codes? Without knowing how these code correspond to the layout, it's nearly impossible.  Can it be done in other ways? 

Any ideas?

 

 

 

 

 

 

Parents
  • skillUser

    Hi Nosaj,

    If you use dbWriteSkill() I do not think that it returns the SKILL that the PCell was originally coded with.  In your pasted code (typical output from dbWriteSkill() I would guess) you can see some rectangles being created - it is highly unlikely to have been coded this way to begin with, more likely this was a dbCreateRect in a looping construct (e.g. a for loop), or even created by something like rodFillBBoxWithRects(). I've not used DumpPcDefinePcell so I cannot comment on it.

    On to your questions. Why are you trying to modify PDK devices?  I would have thought that this should really involve the PDK provider? Attempting to dump out the SKILL to recreate the devices could be seen as reverse engineering and would be frowned upon if not actually illegal.  Besides, if you don't understand the SKILL code, I don't think you should be messing with it!

    Having said this, perhaps one way to "modify" the device would be to make a copy and add to it (if you are simply adding), or better yet, place an instance of the device in a new cell and add the changes in there.  If you need to modify the device by 'removing' or reshaping, then perhaps you can copy the cell (or content using Yank and Paste) and flatten it in order to make the changes.

    Have you contacted the PDK supplier to see if they can help?

    Best regards,

    Lawrence.

Reply
  • skillUser

    Hi Nosaj,

    If you use dbWriteSkill() I do not think that it returns the SKILL that the PCell was originally coded with.  In your pasted code (typical output from dbWriteSkill() I would guess) you can see some rectangles being created - it is highly unlikely to have been coded this way to begin with, more likely this was a dbCreateRect in a looping construct (e.g. a for loop), or even created by something like rodFillBBoxWithRects(). I've not used DumpPcDefinePcell so I cannot comment on it.

    On to your questions. Why are you trying to modify PDK devices?  I would have thought that this should really involve the PDK provider? Attempting to dump out the SKILL to recreate the devices could be seen as reverse engineering and would be frowned upon if not actually illegal.  Besides, if you don't understand the SKILL code, I don't think you should be messing with it!

    Having said this, perhaps one way to "modify" the device would be to make a copy and add to it (if you are simply adding), or better yet, place an instance of the device in a new cell and add the changes in there.  If you need to modify the device by 'removing' or reshaping, then perhaps you can copy the cell (or content using Yank and Paste) and flatten it in order to make the changes.

    Have you contacted the PDK supplier to see if they can help?

    Best regards,

    Lawrence.

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