Siemens SIMATIC S7-1200 Function Manual page 510

Instructions
9.5 Polyline
The following figure shows a polyline with four points.
Call
Polyline is called as a single-instance DB in an OB. In an FB, Polyline can be called as both
a single-instance DB and a multi-instance DB and as a parameter-instance DB.
When the instruction is called, no technology object is created. No parameter assignment
interface or commissioning interface is available. You assign the Polyline parameters directly
in the instance DB and commission Polyline using a watch table of the user program in the
CPU or HMI.
Startup
The tags in the UserData and WorkingData structures are not retentive. These tags are
initialized with the start values after each change of operating state of the CPU from STOP to
RUN.
If you change the actual values in the UserData structure in online mode and these values
are to be retained after the change of operating state of the CPU from STOP to RUN, back
up these values in the start values of the data block.
At the first call of the Polyline instruction after the change of operating state of the CPU from
STOP to RUN, the data in the UserData structure is automatically checked for validity. If the
check is successful, the data is transferred to the WorkingData structure.
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Function Manual, 03/2017, A5E35300227-AC
PID control