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Access Top-Level Hierarchical Net with BSource

FormerMember
FormerMember

Hello,

I am trying to define a bsource within a subcircuit, which addresses currents and voltages from the top-level hierarchy. For currents, this seems to work, but for voltages it does not. My expressions looks like this ('I0' is an instance in the top schematic and 'I1' an instance in 'I0', which has a net 'net1')

for current: i=i(".I0.I1:1") -> works
for voltage v=v(I0.I1.net1) -> does not work

I also tried different variants

v(.I0.I1.net1) -> error because of leading '.'
v("I0.I1.net1") and v(".I0.I1.net1") -> also does not work

It seems, instead of interpreting the voltage path as global, Spectre assumes them as local, because i get warnings for dangling nets with these names.

I searched the Forum and the Spectre reference and user manual, but could not find an example for what I am trying to do. Maybe it is not possible at all, but why does it work for currents?

Best regards
Paul

  • Andrew Beckett

    Paul,

    Apologies for the late reply. I looked into this and found that the support for the current syntax was as a result of CCR 800632 that I filed in response to the forum question: subciruit initiated top-level current probe. This was added in a hotfix for MMSIM7.2 in 2010 some time. However, I don't think anything was done to support a similar mechanism (with a leading dot to indicate starting from the top level) for out-of-module voltages. I've not spotted a request for this, but I didn't spend too long searching so I may have missed it.

    I suggest you contact customer support and request this as an enhancement. I know there are requests to do this with "deepprobe" (which is an iprobe using an out-of-module reference to a hierarchical node name) but it ought to be slightly easier with a bsource voltage expression.

    Regards,

    Andrew

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