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 same net, 2 constraint values 

Last post Thu, Oct 22 2009 10:42 AM by mikem. 1 replies.
Started by skillnewbie 26 Aug 2009 09:43 AM. Topic has 1 replies and 1985 views
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  • Wed, Aug 26 2009 9:43 AM

    same net, 2 constraint values Reply

    Hi all,

    I have a 2 Cline segments of the different width, one is 100 while the other one is 200, they are of the same net (that's say, Net1) and

    they are connected together.

    i also have a dynamic shape of Net2 surrounding the Net1 clines.

    I want to have two different spacing value for the two Net1 cline segments, width 100 -> spacing 150

    and width 200-> spacing 250.

    I created two spacing constraint sets, one is (default) Shape to Line = 150 while the other one (bigger_gap) is 250,

    However, after drawing the constraint area and attach the Net_Spacing property, both portion of the Net1 Clines open a

    gap of 250 with the dynamic shape of Net2, no matter how i adjust the constraint area, it is still the same.

     Any one has got idea how shall i go with this?

    Thanks in advance

    • Post Points: 20
  • Thu, Oct 22 2009 10:42 AM

    • mikem
    • Not Ranked
    • Joined on Mon, Aug 25 2008
    • Posts 7
    • Points 65
    Re: same net, 2 constraint values Locked Reply

    It seems Cadence looks at the entire cline (vs.cline segments), when applying spacing constraints within a region.  This isn't good, but it's what you have to work with.

    Off hand, a quick work around would be to terminate the cline, where the cline width changes inside the constraint region.  For example, route the trace at the width desired inside the constraint region.  Before the cline trace exits this region, place a "via" pad that will serve to terminate the cline.  From this via, change to the alternate line width and continue routing outside the constriant region.

    To make the via, define it on a single routing layer with no drill.  Make the pad size equal to, or less than, the smaller line width.  Simply select this via while routing, to terminate the clines as needed.  Update the shapes and you should have the proper line-to-shape clearance both inside and outside the contraint region. 

    Last step is to ask Cadence to revise the software, so that constraint regions consider cline segments vs. clines.

     

     

    • Post Points: 5
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Started by skillnewbie at 26 Aug 2009 09:43 AM. Topic has 1 replies.