Siemens SIMATIC S7 System Manual page 351

The divergence of control streams can be implemented in an SCR program by using multiple
SCRT instructions enabled by the same transition condition, as shown in the following
example.
Example: SCR divergent flow control
LAD
Convergent flow control
When streams converge, all incoming streams must be complete before the next state is
executed.
The convergence of control streams can be implemented in an SCR program by making the
transition from state L to state L' and by making the transition from state M to state M'. When
both SCR bits representing L' and M' are true, state N is enabled as shown in the following
example.
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
Beginning of state L control re-
gion
S3.5: Transition to state M
S6.5: Transition to state N
End of the state region for state L Network 3
STL
Network 1
LSCR S3.4
Network 2
LD M2.3
A I2.1
SCRT S3.5
SCRT S6.5
SCRE
Program instructions
7.13 Program control
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