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Using the Virtuoso autorouter: routing grid

RVERP

How do I set the routing grid? I can use the option to route on the routing grid, but I can't find how to check it's value, or how to set a new value.

I want to force the autoroute to place spines/vias on the exact grid I want, so I suppose the routing grid is what I have to use.

  • Quek

    Hi RVERP

    Actually Virtuoso has 2 auto-routers (VCAR and VSR). It would be great if you can provide the following details too:

    a. Version of Virtuoso
    terminal>virtuoso -W

    b. Are you using VCAR or VSR?

    Best regards
    Quek

  • RVERP

    Sorry for the delayed answer.

    I'm using version IC6.1.6-64b.500.12, and the space based router.

  • RVERP
    I'm gonna bump this back to the top.
    I still can't make the autorouter route on the grid I choose. FYI, I use VSR in ICS6.1.7-64b.500.4.

    Snap wires is set to Routing Grid. The grid is set with a user defined constraint group (Default horizontal/vertical routing pitch). If I do manual routing, the default grid is followed. If I use finish wire or auto route, the grid is ignored. Any ideas why?
  • ColinSutlieff

    Hi,

    By default, the router is in "hybrid" mode which means that it can go off-grid if there are pins that are placed off-grid.

    But, could you check if you have any routing offsets in your techfile or technology graph (Constraint Manager->Process-rule overrides)?

    Is it possible that the router is putting the routing on grid but ignoring the offsets?

    If so, we may need to investigate this further.

    Colin

  • RVERP
    All the pins are also on the layout grid. The router goes rogue the first turn he has to make, and returns on the routing grid when it connects to the destination pin (since it is on the routing grid). The shapes he has to route around are on the manufacturing grid.
    The default vertical and horizontal offset is set to 0 in the process rule overrides.
    To what is this offset related to? Is it the offset from a nearby shape? That can explain it maybe.
  • ColinSutlieff

    There may be something like this in your techfile:

    routingGrids(
    ( horizontalPitch "Metal2" 0.29 )
    ( verticalPitch "Metal2" 0.29 )
    ( horizontalOffset "Metal2" 0.145 )
    ( verticalOffset "Metal2" 0.145 )
    ) ;routingGrids

    This means that the router should route on a 0.29 grid but with an offset of 0.145.

    This is a very typical situation.

    In other words, it should route on grids of 0.435 0.58 0.725 etc

    The offset is global and has nothing to do with any blockage shapes.

    Regards

    Colin

  • RVERP
    Is the Default horizontal/vertical routing pitch overruling this layer specific pitches?
  • ColinSutlieff

    Hi,

    The routing pitches are determined by a lookup mechanism that starts with the settings that you have in your Wire Editor environment and ends with settings in the Process Rule Override.

    (PRO have the highest priority)

    Because I have no access to your data I will make some guesses (based on a typical setup):

    You have a Constraint Group called "LEFDefaultRouteSpec" defined in your technology library. This contains the routing grid and offset definitions

    You have loaded this constraint in your Wire Assistant.

    You have setup route to "routing grid" and nothing happens........:(

    Here is one last suggestion. If this doesn't work we need to ask you to contact customer support.

    Go to options->Editor

    Look at the section "wire editing (wire)" 

    Make sure that the Default Wire Constraint Group "LEFDefaultRouteSpec" is specified.

    Try routing again.

    Let us know if this works.

    Regards

    Colin

  • RVERP

    Alright, the router is behaving als expected. The problem was that I only had set a default routing grid. When I added metal specific routing pitches, all was fine.

    Probably there are values for this in my tech file, and they were overruling the default (logically).

    The only thing I don't get is that manual wire editing behaved according the default values, while automated routing behaved according the metal specific values.

  • Alex Soyer
    Hello RVERP,

    Could you please confirm that you have set the 'Snap Wires to' to Routing Grid ?

    You could check into the Wire Assistant or in the Options > Editor form 'Wire Snapping'

    Thanks,
    Alex

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