On Tue, Aug 28, 2007 at 09:47:02AM -0700, Kirk Wallace wrote:
> Thank you Ray and Jeff for your replies. I am really going to have to
> allocate some time to CL.
It took me a while to get started with CL, but once I figured out the
basics it was easy going. I found lots of documentation online, but
none of it seemed to be a basic introduction useful for someone like
me (a programmer type who can understand the concepts perfectly well,
but had no experience with ladder diagrams).
If I were to make a cheat sheet, here's what I would put on it. If
you're like me I think it's exactly the summary you need:
Things specific to classicladder:
%I are input to ladder (classicladder.0.in-XX HAL pins)
%Q are outputs of ladder (classicladder.0.out-XX HAL pins)
%B are internal/intermediate signals
Things people who know ladder already know, but I didn't:
-| |- are NO
-|/|- are NC
-|^|- is rising edge
-|v|- is falling edge
-( )- is a "coil" (the rung's output)
A useful configuration used to latch a state:
%I1 %I2 %B1
-+--| |--+--|/|----( )----
| |
| %B1 |
+--| |--+
See how when I1 comes on, B1 turns on which latches the rung on (since
B1 is across I1, it doesn't matter what I1 does now). Then when I2
comes on (remember it is NC because of the /), it breaks the latch and
the rung goes back off.
Once you understand this basic shape it's easy to build up sequential
logic/state machines.
Chris
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