On 2013 Jul 26, at 3:21 PM, Tony Duell wrote:
While one may want to communicate with an author
about more subtle
aspects of their work, this is such a basic thing I see no need for
asking, and waiting, for an answer about it. I can't say it would
even occur to me to ask, as if you have a convention about it, it
I have sene this convention used so many times that it never
occured to
me to describe it.
I have never seen it used previously.
That's a lot of ambiguity and non-obvious rules for a de-facto or
unwritten standard.
OK... Perhaps I should have documented it somewhere.
However, I do stand by my point that checking out the 2 or 3 inputs of a
gate doesn;t take long. And once you've done a a few you might think that
I've been consistnnt...
Anonther convnetion that I stick to (and which is somewhat universal)
relates to grounds :
This :
|
---
///
Means logic 0V, signal common, whatever
This
|
-----
---
-
Keans chassis or mains earth,
And this
|
---
\./
(A triagnle)
means another common rail. I often use that to mean the -ve side of the
mains smoothing capacitors in an SMPSU (not applicable here). Connect
that to mains earth nnd you'll know about it.
And perhaps I should also say that 'xxx means '74xxx'. So 'H108 means
74H108, etc.
I take the position that the primary point of a schematic is to
elucidate the functional, electronic organisation of the device. The
OK,. That is certianly one important use. I don;t think it's the only
one, but...
Hang on a second... If you primarily want to see how the thing works,
then why do you care about the pin numbering of inputs on gates. The
reaon the pins all look the smae on the schematic is that they act the
same -- you can wswap round the inputs to an AND, NAND, etc gate and the
circuit does the same thing. So not knowing my convnetion shouldn't
matter here.
physical implementation is important, but a secondary
consideration.
For somebody repairing a unit, which they are probably doing on a one-
off instance for an RE'd item, the first priority is still that
functional understanding.
So the schematic gets organised with signal flow left to right and
electron flow up the page (for +V systems) as much as possible, and
functional associations as close together as possible, even if that
means bits of one board end up on multiple pages. All within reason
as there are always exceptions.
Sure. I did put -ve at the top of the page on the HP9100 diagrams as that
thing is all PNP transistors and runs off a -15V rail. But in genral I
agree with you.
If you want all the physical associations as close
together as
possible, prioritised over the functional, it becomes a wiring diagram.
I feel the same schemaitc can be used for both. That is, by adopting IC
diagram conventions or numbering the pins, by drawing out connectors, by
putting descriptions of the colours of the wires, etc the same diagram
cna both be a functiuonal diagram and a a wiring diagram
(The pages you are looking at are old, it has since been encapsulated
in a single PDF, updated now.)
OK. I couldn't find this PDF anywhere, it is on the web?
-tony