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 Differences between pins from digital and analog views of a schematic 

Last post Fri, Jan 25 2013 12:08 PM by glennramalho. 3 replies.
Started by glennramalho 22 Jan 2013 06:27 AM. Topic has 3 replies and 974 views
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  • Tue, Jan 22 2013 6:27 AM

    • glennramalho
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    Differences between pins from digital and analog views of a schematic Reply

    Hi,

    I have a mixed schematic, mostly analog but with some embedded digital controllers. The digital parts were made in SystemVerilog and imported into the correct views in virtuoso together with the schematics. Then using RC and Encounter the schematics and layout views were generated and also imported into the database. The problem is some inconsistencies came up.

    RC added pins for scan chain and Encounter had to buffer the clock trees and created the respective pins as well (clk__L1..., etc). These do not show up in the top level of the digital schematics, only between the internal blocks. Being these new pins do not exist in the RTL, anytime I open the SystemVerilog views I get error messages back from the tool stating the pins are not consistent with the symbol. If I just send it all to UltraSim or VerilogAMS with the netlist views it works fine, but when I try to use the SystemVerilog views with the schematics to run VerilogAMS the netlister quits with an error. The netlister will not run if the views do not match even though the SystemVerilog files do not need these extra pins.

    I guess the simplest solution would be to change the RTL by adding these missing pins as dummy pins. A bit anoying as it would start cluttering the design and also would require some manual work after every change to remove the old added pins, add the new ones (as the names change in every run) and recheck all schematics and symbols.Remove the added pins does not sound like a solution either as they are in the layout and therefore LVS is going to expect to find them.

    Being these are not new concepts I would think Cadence already has something in place to handle these issues of mixed environments. Anyone have any ideas?

    -G

    • Post Points: 20
  • Tue, Jan 22 2013 10:06 AM

    • AndreasLenz
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    Re: Differences between pins from digital and analog views of a schematic Reply

    Hello -G,

    which IC and EDI version do you use ? Since you're talking about layout views I assume you work on an Open Access Database.

    Is you're PDK Mixed Signal enabled - means do you have your technology LEF available as an OA library referencing the Base PDK?

     

    Cheers

    Andreas

    • Post Points: 20
  • Tue, Jan 22 2013 2:27 PM

    • glennramalho
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    Re: Differences between pins from digital and analog views of a schematic Reply

    The IC is 6.1.5-64b.500.

    The RTL Compiler is RC10.1.301 - v10.10-s313_1

    TheEDI is version 10.10

    As for the PDK, I am not sure what you mean. We received the PDK from the foundry with LEF, Synopsys files, netlists in CDL and Verilog, etc. As for the database we had to convert the LEF files and library netlists into OA so we could do full-custom analog+digital design. Then all our analog work has been done in OA in schematics and simulated using UltraSim. It is just when digital and analog meet that problems come up.

    From Encounter, I exported the DEF and netlist files. Then imported both into virtuoso using verilogin and defin. When I did that the SystemVerilog views no longer matched the pins of the newly created schematic, symbol and layout views. Then, when using the regular gui invocation for VerilogAMS, I specify to use schematic views and it works great. If I specify that I want the digital subblocks to be using the SystemVerilog views it all dies due to the missing internal pins. And if I open the SystemVerilog RTL and save I get also a message back as the extra clock buffering pins are not in the RTL.

     

    Cheers,

    -G

     

    • Post Points: 5
  • Fri, Jan 25 2013 12:08 PM

    • glennramalho
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    Re: Differences between pins from digital and analog views of a schematic Reply

     I guess there is no automatic way. Cadence support suggested some parameters that killed some functionality and I was hoping for something that would not require changing the view one way that would not require manual effort. Experimenting we came out with a solution that I`ll share here.

     

    * Tell the netlister to use the systemVerilog view for the digital controller top.

    * Inside the ADE netlist options use the Stop View list and add systemVerilog to whatever else is needed for the analog schematics. Then the digital controller will show up as a black box. This eliminates all the internal pin checking. As I said the top level pins match the schematic, it is jsut the internal blocks theat don`t.

    *  Create a directory and inside it create a series of symbolic links. Each one should have as a name a SystemVerilog module. So controller_top.sv would point to .../library/controller_top/systemVerilog/verilog.sv, and controller_core.sv would point to ....../controler_core/systemVerilog/verilog.sv, and so on. (there are other ways to do this as well, via the -f option of irun, or via a file with several include statements)

    * In the simulation options set the libext field to .v,.sv so that both SystemVerilog and Verilog are searched. In the -y field put in the symlinks directory. And also include with the -v or -y fields whatever models that the RTL views might need.

    * Then tell the netlister to run and then start the VerilogAMS simulation.

    Then you would need a netlister configuration for each type of simulation. One for UltraSim using schematics or perhaps VerilogAMS using schematic views. One for VerilogAMS with SystemVerilog, as described above.


    I guess there is still a minor issue that any time I make a change to a systemVerilog view I get an error back when I save it. I probably would have trouble running a pure digital simulation from within virtuoso, but I usually do that from the command line anyways, so no harm there.

     

    Thanks

    -G

    • Post Points: 5
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Started by glennramalho at 22 Jan 2013 06:27 AM. Topic has 3 replies.