Rockwell Automation 1794-Lxxxx PhaseManager - Manual (Page 41)

Publication LOGIX-UM001B-EN-P - April 2010 41
Guidelines Chapter 3
Guideline Details
A PCMD instruction causes a transition
right away. A PCMD instruction makes an equipment phase go to the commanded state. The equipment
phase changes states as soon as it finishes its current scan. This happens even if the current
state isn’t done.
See if you need to reset the state that
you’ve left. Are you leaving an acting state (for example, running, holding)?
• YES — Consider resetting the code of the state that you’ve left.
• NO — You probably don’t need to reset anything.
The equipment phase stops running the code of the current state when it goes to a different
state. This leaves outputs at their last values unless the new state takes control of them. It
also leaves an SFC at the step it was at when the equipment phase changed states.
Example 1: You don’t need to reset
Suppose your equipment phase is in the idle state. In that case, it isn’t running any state code.
So you probably don’t need to reset any state when you go to a different state like running,
stopping, and so forth.
Example 2: You don’t need to reset
Suppose your equipment phase is in the running state and you go to the holding state. When
you go back to the running state, you probably want to pick up where you left off. In that case,
you probably don’t need to reset the code in the running state.
Example 3: You must reset
Suppose your equipment phase is half way through the resetting state and you give the stop
command. And suppose you want to run the entire resetting sequence when you go back to it.
In that case, you probably need to reset the code of the resetting state. If the resetting state
uses an SFC, then use the SFR instruction to reset it to the first step.
Use an SFR instruction to reset the SFC of
a state routine. An SFC Reset (SFR) instruction is one way to reset an SFC. In some cases, reset an SFC from
several other state routines.
To reset the SFC of this
state Place an SFR instruction in this state routine
Running Resetting
Holding Holding—Let the SFC reset itself at the last step.
Restarting Reset the restarting routine in both these routines:
• Holding—In case you go back to holding before you finish
restarting.
• Restarting—Let the SFC reset itself at the last step.
Use the PCMD instruction to go to an
allowed next state. PhaseManager software makes sure that an equipment phase follows the state model. So the
equipment phase goes only to certain states from the state that it is in right now.
Example 1: A transition is allowed
Suppose your equipment phase is in the running state and you give it the hold command. In
that case, the equipment phase goes to holding because that transition is allowed.
Example 2: A transition isn’t allowed
Suppose your equipment phase is in the running state and you give it the reset command. In
that case, the equipment phase stays in the running state. To go to the resetting state, you
first have to stop or abort the equipment phase.