2 Replies Latest reply on Jul 31, 2013 2:03 PM by michael.weinberg

    CES - Assign a value to a variable


      Do I miss something?

      I defined a variable named "somelength"

      On pin-pair "A", formula I wrote "=somelength"

      On another pin-pair, "B", I use the variable in a formula like "=5000-somelength+/-100th"

      The last formula is templated and used on several pin-pairs.

      how can I get a violation on the first formula?

      It is a definition of the value of the variable.


      Second question about tuning.

      Is it reasonable to get tuning constraints violations when the autorouter has plenty of space to tune?




        • 1. Re: CES - Assign a value to a variable

          Hello Larry,


               The variables are used to quickly and easily associate multiple nets/pin-pairs etc together in a similar way to match groups but providing more scope of flexibility. I think that it is probably best to use an example. If I have three nets A,B,C and I add the formula to them using the variable MatchMe then I would see...






               In this example if






               We obviously break the requirement but the question is which one of the nets do we hightlight in error?


               The algorithm is such that it simply trys to solve all the formulas using a value for the variable MatchMe and then highlights those which are outside the tolerance.


               When we have the statement of A=MatchMe we are not setting MatchMe to equal A; what we are setting is that A equals the variable MatchMe and MatchMe will be determined by solving the formula for all nets that use this variable.


               So in your original example where you have A=SomeLength and then B=5000-SomeLength+/-10 it is not setting SomeLength = to the length of A.





          • 2. Re: CES - Assign a value to a variable

            Hi Larry,


            Try leaving out the equals sign when entering formulas.


            Here's another take on matching lengths (from a recent post elsewhere):


            Try this to match length of electrical net to pin pair - image references shown in ():

            1. Set Min and Max Length for the pin pair (Net D)

            2. Enter a Match variable (PINPAIR) and Tolerance (0.5) for the pin pair (Net D)

            3. Enter the Match variable (PINPAIR) for electrical net (A^^^)

            4. Configure the autorouter passes as shown and click "Route" (autoroute result may be improved with addition of Route Obstruct)

            5. Update actuals in CES and review






            Example 1 - Trace Length Matching between Pin-Pair and ENET.jpg

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