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POwer routing : Top level Block PG pin routing

remi pallas

Hello,

I'm using hierarchical methodology. I did block place and route. I generated lef abstract using : write_lef_abstract ./RESULTS/${DESIGN_NAME}_abstract.lef -stripePin -PGPinLayers {2 8} -extractBlockPGPinLayers {2 8} -cutObsMinSpacing

I'm doing power routing and especially want to connected block PG pins with STd cell power rails (row). But I cannot on every block. When doing sroute , some power rails remains open (see the picture).

When doing point to point route , it says on some pins :

**Info: Selected object: "-net {VDD M2 (361.58 242.084)}".

**Info: Selected object: "-pin {-1 VDD (361.444 242.084)}".

**Info: Calling routePointToPoint -routeLayer M2:M2 -width 0.208 -spacing 2.0 -routeStyle manhattan -net {VDD M2 (361.58 242.084)} -pin {-1 VDD (361.444 242.084)}

routePointToPoint ...
>>> Begin point to point routing for 'VDD'
*****************************************************
**WARN: (IMPPPR-445): OPEN in 'VDD' (234.704 242.000)=>(361.850 242.000) because of too much congestion or blockages.
*****************************************************
Net VDD failed to route.
*****************************************************

That's weird because I suppressed all my block routing blockages and  I'm before routing stage.

Maybe there is a congestion problem related to my block's pin ?

Thanks,

Rémi

  • remi pallas

    Hello,

    ALways with my problem of open on my block's PG pins. Sroute cannot afford to route all the Vdd/gnd power rails. You can see in the picture below the white crosses at the boundary of some blocks.

    I found that the problem is related to the way you floorplan your design. I mean block location (I did relative floorplanning) and row density. It seems that in my case increasing row density betters sroute results.

    SO my questions are , in the case of bottom-down hirarchical methodology , how do you floorplan? How do you power route (both top level and block side)?. Is there any rule of thumb?

    Thanks,

    Rémi

  • remi pallas
    in reply to remi pallas

    Hello,

    Right now , I cannot find the cause of my problem (Other collegues got that problem too). So I will use an ugly solution 1234

    -draw ring inside blocks to connect VDD/GND rails .

    -draw  VDD/GND ring around blocks at top level

    -connect rings together using vertical stripes (see the picture)

    Thanks,

    Rémi

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