Siemens SIMATIC S7 - Page 351

Program instructions
7.13 Program control
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
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
STL
Beginning of state L control re-
gion
Network 1
LSCR S3.4
S3.5: Transition to state M
S6.5: Transition to state N
Network 2
LD M2.3
A I2.1
SCRT S3.5
SCRT S6.5
End of the state region for state L
Network 3
SCRE
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.