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Mapping between symbols and ports

Question asked by JKoltner on Sep 15, 2006
Latest reply on Sep 16, 2006 by MZachmann

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I'm noticing that some of the supplied Genesys models -- such as those for the Coilcraft inductors -- use a standard 2 pin inductor symbol but reference a 2 port S parameter data file.

How does Genesys "know" where to tie the reference for the 2 port S parameter data to? Presumably it goes to ground?

The inductor says it uses model TWO, but looking up the on-line help for TWO shows three terminal devices.

Thanks,
---Joel Kolstad

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MZachmann Sep 15, 2006 2:15 PM
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Hi,

Yes, I guess you could say it references to ground. That third port is autogrounded in the symbol.

Mark
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JKoltner Sep 15, 2006 6:00 PM
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"

Yes, I guess you could say it references to ground. That third port is autogrounded in the symbol.

"

Thanks Mark... how would I go about ascertaining this for any old symbol for myself?

---Joel
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JKoltner Sep 15, 2006 6:00 PM
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"

Yes, I guess you could say it references to ground. That third port is autogrounded in the symbol.

"

Thanks Mark... how would I go about ascertaining this for any old symbol for myself?

---Joel
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MZachmann Sep 16, 2006 3:10 AM
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Hi Joel,

I'm not sure of your question. I answered your first question a little too simplistically.

The symbol itself doesn't really autoground (symbols are just pictures) - it's just an indicator that it works with both 2-port and 3-port models.

Personally I prefer using the usual op-ampish 2-port symbol myself when I'm reusing a 2-port dataset - or more commonly doing what you did, which is to apply it to an appropriate symbol such as an inductor.

Mark
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JKoltner Sep 16, 2006 8:12 AM
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Hi Mark,

What I'm trying to figure out is... if I have a symbol with 2 pins that "somehow" gets mapped to a model that has more than 2, how do the ports connect up?

Is it always pin 1 of the symbol goes to port 1 of the model, 2 to 2, etc., and if there are more model ports than symbol pins the rest of the model ports are grounded? Or...?

In schematic capture/PCB layout, I'm used to somewhere having a "part editor" where you make these assocations in something that resembles a spreadsheet. (Often times there are even three columns -- symbol pin, footprint pin, and model pin, or two two column views, etc.)

Feel free to refer me to the built-in help if it discusses this; I didn't find it in the quick searching I already did there.

Thanks for the help -- I think Genesys is seeing a lot of great improvements under your watch.

---Joel
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MZachmann Sep 16, 2006 11:56 AM
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Hi Joel,

First, thanks for the comment. I may be wrong in a few particulars below but generally...

Model and Symbol Mapping:

Let me talk about this from the standpoint of "you" creating a symbol/model. Note that all of our symbols are viewable/editable in the Symbols library (you can't edit that library but you can copy them elsewhere and edit them).

When you create a symbol or a model it has a bunch of ports in it usually. Each port correlates to an "output" terminal. If you name the port, that becomes the name of the terminal. We ignore the default port name (Port_xx). In addition, each port has a number associated with it (the PORT value).

When you associate a model with a symbol the analysis engines use the following logic:

1) If the model has named ports/terminals (a model you built, for example, although some of ours have named terminals) those names are used.

2) If the symbol has named ports we check for correlation with the model names. If it's partially correlated we error out (I think). If it's not at all correlated (one or the other is numeric) we backpedal to using numbers [and pop a warning]. If it's fully correlated we use that association.

3) If uncorrelated or not named we use a numeric association between port numbering. S-data come with port number associations built in, usually. Spice and Verilog-A are named and/or numbered. For models and symbols the numbers come from the PORT value.

4) If the symbol has fewer ports than the model we leave those ports open on the model [and warn].

5) If the symbol has more ports than the model we just ignore the extra ports (they're open) [and warn].

Mark
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MZachmann Sep 16, 2006 12:15 PM
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Hi Joel (part 2)

Viewing Model and Symbol mapping

The schematic netlist is easily visible in three ways. A "net" is a connected piece of the netlist.

a) You can see the net naming on the schematic itself. Usually it's small dark-green numbers at the nodes, but actually nets can have any name you want. You can set the current prefix (it will make netnames prefixxx as you create nets) in Tools Options.

b) Switch to the partlist view and click the top bar then turn on Netlist and view the netlist for each part. The netlist is "symbol terminal name, net name" pairs for each terminal/port. You can not edit it here unless there's no schematic (that would be chaotic). For each net you can see the terminal name for the part - the symbol terminal/port name.

c) Double click a part and look at the netlist page.

The only way to tell what models use for terminal names is by viewing the model itself.

Editing the net mapping

If you have no schematic you can double-click a part in the Partlist and edit the Netlist in the netlist page. This is free-form but similar to the spreadsheet method you describe. If you have a schematic, it must be used to set the Terminal-net connections.

Renaming a net

Currently this is harder than it should be. You do this by right-clicking a connector (only) and selecting Net -> Rename... You can rename them in bulk by using the "Renumber Nodes" command in the schematic menu.

Mark
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Mapping between symbols and ports

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