I have similar (nearly same) issues and concerns about what a schematic should be.
Your statement "I remember Intel used an off-sheet convention on its SBC (Multibus) schematics. Unfortunately, this no longer seems to be practiced, and I know of no current CAD system that provides this option."
I have used most of the systems out there .. currently I am using CADint. It can automatically extract the page(s) where a connection or bus port goes and note it on the schematic at each port . So, if a signal goes to pages 4,12,23 - it will noted on each signal port involved. It would get messy if it tried to document the x-y location for each connection port... on all the other connection ports (single or bus)
Other simple items that used to be taught to engineers:
- no crossing connections! (a missing or hard to see "connection dot" can completely confuse things). All wire connections should be with a "TEE" connection. This is similar to avoiding the use of certain letters for revision control (capital I or O being confused with lower case L or zero).
- as noted by others, If the design is more than 1 page - make the first page a Block diagram, explaining things. I don't see the need (on CADint anyway) to document the actual signals between pages on the block diagram. A simple indication of existance of signals between appropriate pages / sections is generally "good enough". I love "smart" busing. (bit "0" on address bus not confused with bit "0" on data bus)..no need for A0 and D0 to keep them apart.
- Schematics should be able to be read without the CAD system or the need for text searches in PDFs. (first part of comment - please identify every location the signal goes to) Basically, there are still users of the schematics that will be using hard copies (paper).... be nice to these people, make it usable for them, and the end product will be easier for everyone to read.
I won't put up with a CAD system that doesn't give me control of the location (at any resolution I want), font , size of the text on each component. Mirroring a schematic shape shouldn't mirror the text. But not all of us have the option of chosing the system they are using.
No matter how large the library is... I too, end up creating or re-creating most of the schematic symbols. I am just too picky.
When I was at GCA, the company spent something like $100k for aCAD system from Valid Logic Systems. I was the first to use it. Some of the symbols didn;t meet company standard but I used them anyway. I'd come back from the CAD room with C-size schematics. The drafting people hated it because they saw their jobs on the line.
I had that issue at GCA (long out ofbusiness bu that's another story). But previous engineers had put obsolete singe-sourced parts on the BOM and purchasing needed to provide parts for a build. Sometimes there was an acceptable substitite but often not. Redesign time. Kept us engineers in business.
@ antedeluvian Often our guys will use our in-house part number
Back in the bad old days we could not even place a resistor onto the schematic until it had been given a corporate part number and was entered into the CAD library, which caused delays of several days. To plant it on the schematic one had to type in the corporate part number. No such thing as a generic resistor. A fast work-around was to plant them all as 1K resistors then ECO the BOM later. This did not endear engineering to the documentation control people.
I must say I have the same problem in house.Often our guys will use our in-house part number for a component which is meaningless when you are trying to follow the circuit. CD4013 is just so much more helpful that IC01MC14103BC-PB (not a partcularily bad example, but you get my drift).
Schematic symbols: Don't get me started. Too late.
I was EDN Design Ideas editor from 2008 to 2011. Longest three years of my life. EDN was still in print at the time and we had standard circuit symbols. But, schematic software often used different symbols for the same thing, Even for ground and I'm not talking just analog or digital. This was the standard symbol for ground.
But, some schematics came in with jusr one short bar perpendicular to the long line, but others used a angled single bar. When I started, one contributor, whioc sent in schematics almost weekly and was often published, drew all schematics by hand and scanned them. We had to redraw everything to get a consistent style for print. We had art person who redrew the schematics and she understood the any of those symbols meant the same thing. I didn't have to explain. Life was easy, relatively speaking.
When EDN was sold in early 2010, the new owner (not UBM) didn't bring her alsong figuring the existing art department could take over. Wrong! they coudln;t handle schematics. Much to detailed compared to what they were used to. I had to redraw everything so the art people could redraw again. They still often got things wrong.
At this point, a created a PowerPoint file and pasted in symbols. The symbol library also went to the person who was hand drawing schematics. After that he sent me beautiful schematics in powerpoint.
Today, EDN just posts the author'soriginal schematic, sometimes with alittle editing. Michael Dunn has it easy.
Of course, previous DI editors who did the job pre-email remember having to send corrections back to authors through postal mail. So relatively speaking, I had it easy.
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