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Innovus: Routing Quires & General Advice

Anas2023a95

Dear all, 

I'm working on Innovus to place and route a digital design generated by Genus. 

When I look at the auto-routed layout, there are some points at which I think the tool should be able to do a better job (if I correctly direct the tools). 

1) The Pad cells have two pins with the same name. The tool only connects one pin to the power ring. Is there a way to direct the tools to connect both pads? 

2) The strategy used to connect pad circuitry to PG nets is I think the "nearestTarget" strategy. Can I force the tool to use the nearestTarget everywhere except for PG nets, where I want all connections to be made directly to the power rings? 

sroute -connect { blockPin corePin padPin padRing floatingStripe } -layerChangeRange { M1 M5 } -blockPinTarget { nearestTarget } -padPinPortConnect { allPort oneGeom } -padPinTarget { nearestTarget } -corePinTarget { firstAfterRowEnd } -floatingStripeTarget { blockring padring stripe ringpin blockpin followpin } -allowJogging 1 -crossoverViaLayerRange { M1 M5 } -nets { VDD VSS } -allowLayerChange 1 -blockPin useLef -targetViaLayerRange { M1 M5 }

3) Should the PG and CLK signals be on a specific layer? I'm planning to have those signals on Metal5 as it should have the lowest capacitance in a 5M process, right? 

Please feel free to share your general advice to someone working on his first chip ^_^ 

Many thanks 

Anas

Parents

  • Hi,
    1) This depends on how the pad ports are defined. In the LEF syntax, you have a logical pin, which can have multiple ports, which in turn can have multiple shapes.
    If the two shapes belong to the same port (see example below), the router will connect only to one. If there are two separate ports, you can use the pin rule "must join all ports" to specify that all ports must be connected individually. You can create a must join all ports rule by using the following property definition for a pin : PROPERTY LEF58_MUSTJOINALLPORTS "MUSTJOINALLPORTS; ". You can check the LEF/DEF reference for more details.
    I do not know if the special router (sRoute) honors this property, though.

    2) I am not sure what exactly you are trying to achieve, the screenshot appears to contain signal routing. The special router is only intended for routing power nets.
    You can also invoke it with a limited list of objects to route, e.g. "-connect { padPin }", so that the switches you add to the command only relate to these connections.

    3) Generally you want to have a low-ohmic PG grid to reduce IR drop. This typically implies using some thick wires on the higher metal layers for global power distribution.
    The same applies for the clock signals - you want to reduce RC delay on nets, and this naturally leads to using the higher metals for signals crossing large distances, such as clock.
    But your mileage may vary depending on the design in hand and technology node.

    # Two shapes of same port
    PORT
     LAYER M1 ;
     RECT 1 1 2 2 ;
     RECT 4 4 5 5 ;
    END

    # Two separate ports
    PORT
     LAYER M1 ;
     RECT 1 1 2 2 ;
    END
    PORT
     LAYER M1 ;
     RECT 4 4 5 5 ;
    END

Reply

  • Hi,
    1) This depends on how the pad ports are defined. In the LEF syntax, you have a logical pin, which can have multiple ports, which in turn can have multiple shapes.
    If the two shapes belong to the same port (see example below), the router will connect only to one. If there are two separate ports, you can use the pin rule "must join all ports" to specify that all ports must be connected individually. You can create a must join all ports rule by using the following property definition for a pin : PROPERTY LEF58_MUSTJOINALLPORTS "MUSTJOINALLPORTS; ". You can check the LEF/DEF reference for more details.
    I do not know if the special router (sRoute) honors this property, though.

    2) I am not sure what exactly you are trying to achieve, the screenshot appears to contain signal routing. The special router is only intended for routing power nets.
    You can also invoke it with a limited list of objects to route, e.g. "-connect { padPin }", so that the switches you add to the command only relate to these connections.

    3) Generally you want to have a low-ohmic PG grid to reduce IR drop. This typically implies using some thick wires on the higher metal layers for global power distribution.
    The same applies for the clock signals - you want to reduce RC delay on nets, and this naturally leads to using the higher metals for signals crossing large distances, such as clock.
    But your mileage may vary depending on the design in hand and technology node.

    # Two shapes of same port
    PORT
     LAYER M1 ;
     RECT 1 1 2 2 ;
     RECT 4 4 5 5 ;
    END

    # Two separate ports
    PORT
     LAYER M1 ;
     RECT 1 1 2 2 ;
    END
    PORT
     LAYER M1 ;
     RECT 4 4 5 5 ;
    END

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