Rockwell Automation 1794-Lxxxx PhaseManager - Manual (Page 13)

Publication LOGIX-UM001B-EN-P - April 2010 13
Introduction Chapter 1
One common objection to a state model is that it doesn't fit all equipment.
You may hear or think: ‘My equipment is very complex. There's a lot of
synchronization and many things happen in parallel.’
Keep in mind that a state model looks at your equipment at a very general
level. Different equipment does different things and needs specific code for
everything it does. A state model simply gives you a higher-level framework for
your code.
• The state model defines the general behavior, commands, and status of
the equipment.
• You program the details of the equipment within that framework.
Equipment States The use of a state model may sound like a big change for programmers. But it's
simply a different way to look at the same control problem.
With a state model, you define the behavior of your equipment and put it into
a brief functional specification. In this way you show what happens and when
it happens.
For this State Ask
Stopped What happens when you turn on power?
Resetting How does the equipment get ready to run?
Idle How do you tell that the equipment is ready to run?
Running What does the equipment do to make product?
Holding How does the equipment temporarily stop making product without
making scrap?
Held How do you tell if the equipment is safely holding?
Restarting How does the equipment resume production after holding?
Complete How do you tell when the equipment is done with what it had to do?
Stopping What happens during an normal shutdown?
Aborting How does the equipment shutdown if a fault or failure happens?
Aborted How do you tell if the equipment is safely shutdown?