Can I get a hand with this inverter loop simulation: https://github.com/mattvenn/instrumented_adder/blob/sim-inverter-loop/docs/sim.md ngspice fails to converge

I would first look into this warning

Warning: singular matrix:  check nodes reset and reset

Do you have an idea why this could be?

where was that warning?!

The warning was right in the spice output file that you linked: https://github.com/mattvenn/instrumented_adder/blob/sim-inverter-loop/spice/spice.log If sim fails that is the first thing I check, a somehow malformed netlist.

thanks Harald

@Matt Venn i see in the adder netlist some nodes have escapes on brackets , some haven't, like:

outputs[1] _15_/X

buffers\[5\]/A

So it seems the naming is a bit inconsistent. However this is not the problem, i think. Another issue to consider, in the

instrumented_adder.spice

file the

reset

pin is only declared in the .subckt line and never used, so it seems no resettable flops are used in the design.

Thanks Stefan, yes we figured it out, the rst line wasn't connected

@Matt Venn sorry, the reset issue is a false flag, it is used, indeed.

I fixed it last night, its working as expected now