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avoiding cells with multiple inputs

designer

Hi All,

When I synthesize a design with RC, it uses some library cells which have multiple inputs (e.g. AND-OR combinations with 4 inputs). When all the inputs are not required, RC connects the unused inputs to constant 0/1. Since these constants are connected to lib cells, they can not be removed by the delete_unloaded_undriven command. On the other hand I don't want to use TiHi/Lo cells for these unused pins. Is there a way to direct the RC to avoid using lib cells with multiple inputs, when all their inputs are not used?

 Thank you in advance,

Masoud 

Parents

  •  Hi Masoud,

    as far as I know RC should not waste a larger cell the way you are describing. If RC uses a 3-input OR and one of them is a logic zero, then RC would normally swap it for a a 2-input OR. You may want to take a closer look at the RTL and scripts or post to the Logic Design forum and hope some RC user has the answer for you.

     

    gh-

Reply

  •  Hi Masoud,

    as far as I know RC should not waste a larger cell the way you are describing. If RC uses a 3-input OR and one of them is a logic zero, then RC would normally swap it for a a 2-input OR. You may want to take a closer look at the RTL and scripts or post to the Logic Design forum and hope some RC user has the answer for you.

     

    gh-

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