18 Jun
2011
18 Jun
'11
1:50 p.m.
However, I increasingly run across schematics where a
number of
packages are drawn with tags on almost all leads. Somehow, to get
an idea of the logic flow, you're expected to map out the connections
I find it quite helpful to have major funcional blocks (control
sequencer, accumualator input gating, etc) drawn essentially semarate
with named signals goin in and out. Provided those names are
well-chosing. A name like 'muClk' (Microcode clock) is fine. But when
some 'genius' decided to call the signals AA, AB, AC, ... AZ, BA, BB, BC
etc. it gets painful.
You can also go too far the otehr way. It often helps _not_ to draw in
all the pwoer and groudn rails, for example, but to have a marker for
each one like
+5V
---
|
Othwies the power and gorund lines clutter up the schematic. And I do
find that when you have many unlabbled lines running paralell to each
otehr across a large scheamtic it can be very hard to make sure you're
following the right one.
As with most things there's a balance between drawing i nthe connections
and breakign them and giving them sensible names.
in your head, or use colored ink to connect the points
until a real
schematic emerges. About half of the time, I simply give up and draw
my own schematic.
Inevitably, these are the result of some CAD schematic-with-PCB EDA
tool. Curiously, I've never seen an EDA tool to convert this stuff
into more conventionally human-readable schematic form.
Maybe they're not intended to be read by people, but merely serve as
a reference from which to construct netlists, but I'd still like to
see the guy who figured it was a good thing get his come-uppance.
I find virtually all CAD-prodsuced schematics to be very hard to follow.
I am not sure why, but I much prefer the scheamtics of the 1970s to those
produced today. And don't get me started on the multi-colour schematics
prosduced by some CAD systems where ICs are one colour, passives are
another colour, wires are a 3rd colour and so on.
-tony