OpenLane question: Can I somehow provide port numbers in the OL/OL2 flow so that the terminals in the extracted SPICE netlist are not all mixed-up? @donn @Tim Edwards

If you have a netlist for which you want to match the port order, the method in magic is to use

readspice

to read in the netlist while you have the layout loaded, and the pins in the layout will be matched to the netlist and the ports ordered to match. There are similar methods to annotate layouts from other formats; doing a

lef read

on top of a layout will annotate the ports with LEF pin properties like use and direction.

@Tim Edwards good to know! 🙂 Magic is a treasure trove of features, documentation could be better 😉 @donn any way to use this with

OL2

?

@Harald Pretl: Nearly every day. Once I nearly pulled the trigger on it. . .

@Harald Pretl not without a custom step; integrating this into Magic.StreamOut is on the table tho

@donn That would be really helpful, currently this is a real pain when simulating SPICE netlists coming out of OL2 in an

xschem

testbench.

@Harald Pretl Can you use a wrapper? For example, Test bench top level would look like this and you’d just switch between

X0

instances.

.subckt test_circuitA
X0 A B C D circuitA_wrapper
.ends

.subckt circuitA_wrapper A B C D
X0 A B C D circuitA_xschem
*X0 D C B A circuitA_extracted
.ends

.subckt circuitA_xschem A B C D
...
.ends

.subckt circuitA_extracted D C B A
...
.ends

Or you could wrap the extracted circuit so it looks like a the source and switch includes

.include xschem/circuitA.spice
* .include ext/circuitA.spice

where

ext/circuitA.spice

is

.subckt circuitA .....
* pin order the same as xschem
X0 ..... CircuitA_ext
* pin order from extracted file
.ends

.include ext/CircuitA_ext.spice

@Mitch Bailey: The point is that that shouldn't be necessary and that we have tools and methods to ensure that the order of subcircuit ports is consistent across views. It's one thing to say that you can hand-edit a testbench of a circuit with four ports. Try that with a circuit with 200 ports.

I understand that reordering ports is not something to do manually. My suggestion was to copy the subcircuit header from the extracted file, as is, and change it to an instance line in the wrapper. You wouldn’t need to reorder the ports since within a subckt, spice connects by name.

@Mitch Bailey I think that would work, but I’ll wait until we have a proper procedure. One golden reference should be plugged into all the relevant places to have consistent port ordering everywhere 😀