Essentially a weak connection is one of the pin connectivity models in the OpenAccess database. There are various ways you can describe pin connectivity if you have multiple connection points: Strong connect: This is where you have a single terminal and single pin object in the database, but multiple pin figures. All figures (shapes) on the same pin are deemed to be strongly connected to each other, and so you can connect to any one of them, or more than one of them and the connection can be made through the pin figures. A classic example would be a supply track with a pin figure at the left and right end (these two shapes would be on the same pin object). It's then OK to use the metal connection within the cell to route through the cell. Weak connect: This is where you have a single terminal, but multiple pin objects (each with a single pin figure, although you could have multiple pin shapes if you they are strongly connected between that set of shapes). A classic example of this would be the gate of a MOS device - the top and bottom ends of the poly are separate pins and so are deemed to be weakly connected. Virtuoso XL would allow you to connect to one end or the other, but not both - because you might end up relying on a resistive connection between the two. Must connect: This is where you have two separate terminals (because they are really on different nets) but they are marked as being "must connect". So in other words, the circuit relies on both connections being made externally. I suspect what has happened is that you have a block which has more than one pin for a (clock?) signal and these have been created without care about the pin type, and yet you've connected to both pins. Layout XL will see these as illegal weak connects, and complain about it. LVS doesn't really check this - so it may well be OK (e.g. if there's a metal connection within the block, it's not electrically a weak connection). You can probably fix it by altering the pins within the block to be strongly connected, but I'm guessing here because I can't know for certain without seeing what you've got. So customer support would be your best option here so that an application engineer can look at your layout database with you. Regards, Andrew
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