At 11:34 AM 7/24/2003, Brad Velander wrote:
In this one sheet that was quite packed with components, we removed a purchased bandpass filter that was represented as a schematic symbol block with a few pins, it was in the middle of the packed schematic sheet. In it's place I stuck a small sheet symbol to replace the bought component with a sheet containing a discrete filter design. There was no room to add the schematic components on the main sheet and I figured the sheet symbol would fit within the space formerly occupied by the bandpass filter symbol. The sheet symbol had two ports, "in" and "out", I did the lower sheet with two port symbols "in" and "out" then added the discrete bandpass filter design.

The plot thickens. Brad, you did not state whether or not you ran ERC on the schematic and what the result was when you did.

If the original component symbol had pins that were off-grid, the wires, placed with snap on, might have wired to them, but then the wire endpoints would be off-grid and would remain so when the symbol was deleted. Then when you placed the sheet symbol, the sheet entries (they are not called "ports" -- they connect to ports on the represented sheet) would not be making contact with the wires. To make sure this is not the problem, delete the wires and redraw them with snap on.

So what I was doing was trying to connect the circuit through the two ports, maintain my global power nets (not hidden) and I did this twice for two filters. I set my connectivity to Net Labels and Ports Global. One would expect this to work, I was using global nets (works all the time for me) and I was using wired sheet entries and port symbols (note I wasn't relying on ports being global or anything of the sort, just straight wired connections).

Net Labels and Ports Global will work if you have no duplicated names. The power of using more restricted connectivity is that you can have design re-use and not worry about duplicated names (except for power ports, which are global always).

If you were doing this for two filters using all nets global, then you were forced to give the sheet entries unique names. I think. It gets complicated, I have to think about it more, because ports and sheet entries do not, per se, name nets, as Mr. Wilson pointed out. At least they don't in 99SE.

A sheet entry functions like a wire going from the sheet entry's hot spot to the port with the same name on the named subsheet. As such, it does not establish a net name. To cause a net to be named in a way that you can control, you must name the net on the highest level on which it occurs. Naming it on the subsheet does *not* name it globally. Unless you have net labels and ports global. In which case you didn't need the sheet entry/sheet symbol, nor the port symbol.

I think I said the most important thing at the beginning of the last paragraph. Sheet Entries and Ports, used together, are a very different animal from net labels. When you have net labels and ports global, as I recall, ports function just like net labels. What this does to sheet entries I'm not sure, I unfortunately don't have time to check it out as I would normally do.

Well according to my experience and Craig's comments it doesn't work. This was my recollection as well but wanted to refresh my memory amongst the gang. It baffles me because I had the ports wired, so why didn't they work? They weren't relying on the global connectivity. Another Protel programming genius at work? Ports Global means don't connect ports?

Ports Global means -- as I recall, I'd love to verify it -- that Ports become just another way of labelling a net.

If you are accustomed to working flat, you have net labels and/or ports that must be global. In this case you don't have the option of using more restricted connectivity. That's a problem.

If you have Ports Global, a net should be created from the named Port on the subsheet. In order to connect to that net, you may need a net label or port on the supersheet.

The normal way to use a subsheet the way you intended is to place the symbol with sheet entries (entry and port electrical types affect ERC but not connectivity) wired as if the sheet symbol were a component symbol. You don't need net names on the nets. *both symbols (for both instances) would be identical*. On the subsheets -- and you'd have two of them, both identical but with different reference designators, of course -- you'd have ports matching the sheet entry names. and your connectivity would be sheet entry/port connections. If you want to control the net names, you'd place net labels on the wires on the top level; these, of course, would be distinct.

I'll emphasize that the port names on the two subsheets would be the same. The only thing that is different is the names of the sheets, which, of course, are called out on the sheet symbols on the top level. This is really easy to implement, that is why it is done this way.

It's what happens when Ports are global that I don't know. Where does this leave Sheet Entries? Do they also become global?

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* To post a message: mailto:[EMAIL PROTECTED]
* To leave this list visit:
* Contact the list manager:
* Forum Guidelines Rules:
* Browse or Search previous postings:
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Reply via email to