Please see below.
dan
Thanks Dan for your answer.
>>>You’re welcome.
I have some more points/questions:
1. I don't use global nets. Every net is local to a SUBCKT, the same applies to the top_level_port.
>>>To make this work, your top-level net should be declared as a global.
2. As I said, my *.CONNECT lines are inside the top-level SUBCKT.
>>> Flattened net names do not exist at the level of the subcircuit in which you are placing the *.CONNECT.
>>> Another way to say this is, *.CONNECT does not figure out flattened net paths and make the connections accordingly. It simply looks at the net name, like “inst1/sub_cell_inst/sub_cell_port” and tries to make a connection to that net in the scope of the subcircuit where the *.CONNECT occurs. But no such net exists in your design by that name at that level of the hierarchy. So no connection occurs.
I understand that the netlist is still hierarchical, even though the layout is flat. That is why my *.CONNECT lines have slashes in them, to go through the hierarchy in order to connect to the signal inst1/sub_cell_inst/sub_cell_port. In this case, the top-level SUB has an instance inst1, which in turn has another instance sub_cell_inst, which has a port sub_cell_port, which connects to the net net_to_sub_cell_port inside inst1.
>>> Your source cannot have flattened net names for the reason stated above. Declare the nets in hierarchical fashion and just let the tool figure out the matches to the corresponding flattened nets in the layout.
3. I need to find a way to let Calibre consider the sub_cell_port of sub_cell_inst inside inst1 to be connected to the top_level_port of my top-level SUBCKT for LVS.
dan_liddell wrote:
Note this says the shorts propagate up the hierarchy, but nothing is said about down the hierarchy.
That is definitely an interesting point. Would this imply that you can't use *.CONNECT to connect two nets in different levels of hierarchy?
>>> No, it means you have to connect the nets from the bottom-up, not the top-down. So you have to place the *.CONNECT within the lower-level block where you want the deep short to occur, using a local net and a top-level port name declared as a global.
I doubt it, first because I think this is an important feature and second because I think what they meant is that if you have a down the hierarchy in which a *.CONNECT is used to connect two ports which are separate nets in the instantiating SUBCKT, it will (naturally) short those two (seemingly separate nets) up in the hierarchy as well.
.SUB cell1 a b*.CONNECT a b.ENDS.SUB top_level c dxinst1 c d cell1.ENDS
In my opinion, what that means that in the sample above, in the top_level SUBCKT nets c and d are shorted because of the *.CONNECT in cell1.
>>> You have shorted nets within the scope of cell1 and that will apply going up the hierarchy. But you cannot accomplish the same thing by going down the hierarchy from the top level, like this:
.SUB top_level c d*.CONNECT inst1/a inst1/b $$ this is incorrect because these nets don’t exist here.xinst1 c d cell1.ENDS
To clarify what I need to do, here follows the example I was talking about:
$$ note the following subcircuit
.SUB sub_cell sub_cell_port*.J top_level_port sub_cell_port $$ make the connection going up the hierarchy to the global net.ENDS.SUB cell1xsub_cell_inst net_to_sub_cell_port sub_cell* other instances/primitives.ENDS$$ add this
.global top_level_port
.SUB top_level top_level_portxinst1 cell1* other instances/primitives.ENDS
My question: how should a *.CONNECT look like and where should it be located in order to connect top_level_port to sub_cell_port?
>>> Please try the *.J statement in sub_cell above together with the .global declaration.