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Conformal

archive 

I have run into an issue: there is an 8-bit
input bus.  The 4 MSBs and the 4 LSBs are related: the LSBs are simply the
inversion of the MSBs.  So sel[7] = ~sel[3], sel[6] = ~sel[2], etc.

The original code used all 8 bits of sel (for reasons that I can only
guess).  There isn't any reason to do this in the behavioral code, and in
fact it makes the code a lot less readable.  The problem is that sel is an
input port, so LEC won't pass unless either:
  1. I use sel the way it was used in the original code
  2. I can tell Conformal the relationship between sel[7:4] and
sel[3:0].

Do anyone know a way to achieve the second option?  I'd guess that conformal
supports this, but I have no idea how.

Thanks,
Prasad


Originally posted in cdnusers.org by anssprasad
Parents

  • Hi Prasad

    Here's one way to handle it in Conformal:

    add pin constraint one_hot sel[7] sel[3] -golden
    add pin constraint one_hot sel[6] sel[2] -golden
    add pin constraint one_hot sel[5] sel[1] -golden
    add pin constraint one_hot sel[4] sel[0] -golden

    With these set then logic like this would pass:

    golden
    assign out1 = sel[7]&sel[3] | sel[6]&sel[2] | sel[5]&sel[1] | sel[4]&sel[0];

    revised
    assign out1 = 1'b0;

    Chrystian


    Originally posted in cdnusers.org by croy
Reply

  • Hi Prasad

    Here's one way to handle it in Conformal:

    add pin constraint one_hot sel[7] sel[3] -golden
    add pin constraint one_hot sel[6] sel[2] -golden
    add pin constraint one_hot sel[5] sel[1] -golden
    add pin constraint one_hot sel[4] sel[0] -golden

    With these set then logic like this would pass:

    golden
    assign out1 = sel[7]&sel[3] | sel[6]&sel[2] | sel[5]&sel[1] | sel[4]&sel[0];

    revised
    assign out1 = 1'b0;

    Chrystian


    Originally posted in cdnusers.org by croy
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