1756-PM003H-EN-E, SFC and ST Programming Languages ...

Force Logic Elements 13-11
• To leave a simultaneous branch, the last step of each path must
execute at least one time and the transition below the branch
must be true.
• Forcing a path false prevents the SFC from entering a path and
executing its steps.
• When you remove or disable the force, the SFC can execute the
steps in the path.
Add an SFC Force
To override the logic of an SFC, use an SFC force:
ATTENTION
!
Forcing can cause unexpected machine motion that could injure personnel.
Before you use a force, determine how the force will effect your machine or
process and keep personnel away from the machine area.
• Enabling SFC forces causes your machine or process to go to a different
state or phase.
• If forces are enabled and you install a force, the new force immediately
takes effect.
1. What is the state of the SFC Forces indicator?
If:
off
flashing
solid
Then note:
No SFC forces currently exist.
No SFC forces are active. But at least one force already exists in your
project. When you enable SFC forces, all existing SFC forces will also
take effect.
SFC forces are enabled (active). When you install (add) a force, it
immediately takes effect.
2. Open the SFC routine.
3. Right-click the transition or start of a simultaneous path that you
want to force, and choose either Force TRUE (only for a
transition) or Force FALSE.
4. Are SFC forces enabled? (See step 1.)
If:
no
yes
Then:
From the Logic menu, choose SFC Forcing > Enable All SFC Forces. Then
choose Yes to confirm.
Stop.
Publication 1756-PM003H-EN-E (excerpt from 1756-PM001H-EN-P) - August 2005