At 09:58 AM 5/4/2004, John A. Ross [Design] wrote:
I have had a few discussions previously on this list about the
connectivity models within 99SE and how I have had in some cases seen
errors where power ports are not treated as global when using Sheet
Symbols/Port connections.


Haven't seen that. Suspicious....


Before committing the last of my larger designs to 2004 I would like to
track down the error of my ways.

Excellent idea.


Some screenshots here
http://www.proteluser.com/bbs/showthread.php?p=68#post68

A short summary is that the design has one parent sheet and the rest are
child sheets. [...] Connectivity model is set to sheet
Symbol / Port connections as it should be.[...]

You have Descend into Sheet Parts enabled. This is not what you might expect from the name. A Sheet Part is a subsheet that descends from a component. I've never used one, and you probably aren't either. But this setting can cause a number of weird problems, depending perhaps on the components you have used.


You might also enable Append Sheet Numbers to Local Nets. With the connectivity you are using, you don't intend for any local nets to be connected to a local net of the same name on the other sheet. What Protel will do, as I recall, if such nets exist, is to create separate nets in the netlist, with the same name. This can also cause weird problems.... This may be related, if for some reason Protel is not recognising your power ports as global. At least you'll know!

But Update PCB fails with errors. If previewed it wants to rip up the
power nets completely.

If I generate a netlist and then try to load it manually I get a similar
issue but with more detail, this time the power nets are ripped up and I
get netlist load errors 'net already exists' as it tries to add many
instances of the same power net name (one instance per sheet).

Yup. It is treating them as local. Change the settings as I suggested and see what happens.



If I add a sheet entry to each sheet symbol with the name of the power
net and as a sheet port to the child sheets all is happy, no errors.

Yes, this forces the nets to be treated as sheet entry/port connections.


My understanding was always that power ports were always global, but I
seem to have an exception here, unless I cannot see the wood for the
trees.

I didn't think it would make a difference, but do the power nets exist on the top level schematic? Normally, I'd put any outside-world connections on the top level, including power.


You should not have to place ports on the sheets to connect power, though.... I think fixing those settings will either solve the problem or show us better where it lies. What you did not show in the images is what is on the child sheets....




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