On 01:06 AM 14/11/2003, Protel Hell said:Hi all,
Protel DXP newbie here, many years using other CAD tools (PADS, Orcad mainly), with basic question:
what is the difference between ports & offpage connectors, when is each used and why? what advantage does one have over the other?
Ports are the normal sort means of connecting signals from one sheet to another in Protel products (assuming you are not using a Ports Global naming scheme). Off sheet connectors are provided mainly to provide support for Orcad imports, I understand. They are new in DXP. Unless you expect to be going back and forth to Orcad you can probably stay with ports.
Many DXP designs will use only ports. Off sheet connectors are more rarely used. There has been quite a bit of discussion of the off sheet connector and when and how to use it on the DXP forum. I just tried searching the archive but couldn't find the stuff I am sure is there. There seem to be some problems with searching the archive.
Some more info. The DXP forum can't seem to search back far enough to find these replies so I dug them out of my own email archive.
The following quote is from an Altium employee. I won't mention names but since it is available, at least theoretically, on the public DXP forum I don't think there should be a problem quoting here:
Say you created a hierarchical design, meaning that your regular ports don't connect sheets in a flat way, but vertically up to sheet entries on their parent sheets. Then suppose that one of your sheets grew too big, and you wanted to divide it into two or more sheets, but you wanted them to be treated like one sheet. This is what off-sheet connectors can do: they can create a subsection of flat connectivity within a greater hierarchical design.
Read the Net Connectivity and Navigation article, esp. the part on Grouped Sheets. Notice that you group sheets by pointing the sheet symbol at multiple sheets, separated by semicolons.
Our primary motivation for adding Off-Sheet Connectors was to facilitate imports of OrCAD designs into nVisage.
Later the further qualification was added:
Benefits of off-sheet connectors over ports? You usually don't have a choice to use one over the other. But I guess if I had a hierarchical schematic set up, and I wanted to plug in a multi-page subcircuit that was designed using flat (ports global) connectivity, I'd like the fact that I didn't have to restructure the subcircuit design to fit into the hierarchy. Instead, I could just replace its ports with off-sheet connectors, then place a single sheet symbol in the greater hierarchy that references all of the sheets in the subcircuit design. (By the way, that's what a sub-divided sheet symbol is referring to: single sheet symbol, multiple sheet names).
I guess the way to think of off-sheet connectors is that they give you a limited scope of flat connectivity in a vertical world. But really, we didn't add this new feature to radically revise the way users design their projects. It was primarily a means of maintaining connectivity in the schematics imported from OrCAD.
I have not read the Net Connectivity and Navigation article, so I don't know if it makes much mention of off-sheet connectors.
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