Stats

  • Locked Locked
  • Replies 2
  • Subscribers 65
  • Views 17314
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Expression coverage understanding

Prachi1
Hi, I am running and analysing expression coverage. There I see that there are some expression with '!' or '~' (logical or bit negate), I do not understand how iccr evaluates it. e.g. diffxy = (~(x-y)) + 1'b1; index hit ---------------------------- 2 0 0 Here value of expression 1 is '0', is it value of x-y or (~(x-y). x is 16 bit vector. I tried all the possible values of x and y but I am not able to hit this condition. can some highlight the issue? Regards, Prachi
Parents

  • We don't really know enough to completely answer your question. So I'll make a couple of general comments. By default, iccr scores each term in an expression as if it could take on 2 possible values, 0 or non-zero. So even though the term (~(x-y)) might have 16 bits, unless you say otherwise, the report will only look for a time where it is zero and a time where it is non-zero.

    I plugged it into a small testcase. When x & y were both equal, I hit the 0 term and when they differed, I hit the 1 term.

    Line    Coverage         Expression description
    --------------------------------------------------------------------------------   

    6 100% (2/2)         assign diffxy = (~(x-y)) + 1'b1;

                ( ~(x - y) ) + 1'b1
                 <---1--->

                  hit | <1>
               ! -----------
                    1 |  1
                    1 |  0

    In your simulation, does 'x' ever equal 'y'? If so, you should hit the 0 term for expression 1.

Reply

  • We don't really know enough to completely answer your question. So I'll make a couple of general comments. By default, iccr scores each term in an expression as if it could take on 2 possible values, 0 or non-zero. So even though the term (~(x-y)) might have 16 bits, unless you say otherwise, the report will only look for a time where it is zero and a time where it is non-zero.

    I plugged it into a small testcase. When x & y were both equal, I hit the 0 term and when they differed, I hit the 1 term.

    Line    Coverage         Expression description
    --------------------------------------------------------------------------------   

    6 100% (2/2)         assign diffxy = (~(x-y)) + 1'b1;

                ( ~(x - y) ) + 1'b1
                 <---1--->

                  hit | <1>
               ! -----------
                    1 |  1
                    1 |  0

    In your simulation, does 'x' ever equal 'y'? If so, you should hit the 0 term for expression 1.

Children
No Data

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.