Experimental Physics and
Industrial Control System

"Redman, Russell" <[email protected]> · Thu, 27 Apr 2006 16:36:00 -0400

Dear Emmanuel,

As you mention, this particular problem is simple enough that it
probably should be done in the database, except that it will also make a
good introduction to SNL.  In my own work, I made the decision to use
SNL based on three criteria:

1) Complicated logic - SNL is very good at describing complicated
transition logic, but the same logic encoded in records quickly becomes
impossible to understand.

2) Timeouts - These are easy to implement in SNL, even if the length of
the timeout changes depending on the state of the IOC.  This is often
much harder to do using records.

3) Error messages - If you want dignostic messages to appear on the
console and in the logs, it is easy to generate them in SNL.  This is
not a sufficient reason to use SNL.  There are other tools that can also
manage error conditions, such as the alarm handler.  However, if you
already are using SNL, it is an excellent way to introduce context
sensitive, highly informative debugging and error messages.

Do read the manual.  It is pretty clear and should get you going very
quickly.

Cheers,
Russell O. Redman

-----Original Message-----
From: Emmanuel Mayssat [mailto:[email protected]] 
Sent: Thursday, April 27, 2006 12:36 PM
To: EPICS-tech-talk
Subject: Sequencer intro needed !

Hello,

I am not familiar with the epics sequencer.
I would like to control for the following:
If analog output0 is below 4
then set analog output1 to 30
and analog output2 to 25

I have process variables for all those values.

With EPICS records to do the above, I can use a 
calc + a fanout + a sequencer.

But why not use this simple state diagram to be introduced to state
notation language and the epics sequencer ? 
I have the SNL & Seq user's guide. ( but I never opened it)
I do not know anything about SNL and Seq, but I understand state
diagrams. I have the epics base and a few extensions (if the sequencer
needs to be installed then it is most likely not installed) I am not
stupid (strong assumption here ;-) and can learn new things at an normal
pace

How long will it take me to do the above with the epics sequencer? Is
there another method to accomplish what I want to do? Thanks,

-- 
Emmanuel Mayssat
Cell: 650/793-0626
Lyncean Technologies, Inc.
"See the invisible"

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System