Example Of Sequence Control Relays (Scrs) For Simatic Lad, Stl, And Fbd - Siemens SIMATIC S7-200 System Manual

SCR Example
Figure 9-58 shows an example of the operation of SCRs.
In this example, the first scan bit SM0.1 is used to set S0.1, which will be the
active State 1 on the first scan.
After a 2-second delay, T37 causes a transition to State 2. This transition
deactivates the State 1 SCR (S0.1) segment and activates the State 2 SCR
(S0.2) segment.
Network 1
SM0.1
Network 2
Network 3
SM0.0
Network 4
T37
Network 5
Figure 9-58
S7-200 Programmable Controller System Manual
A5E00066097-02
LAD
S0.1
S
1
S0.1
SCR
Q0.4
S
1
Q0.5
R
2
T37
TON
IN
20
PT
S0.2
SCRT
SCRE
(Program continued on next page)
Example of Sequence Control Relays (SCRs) for SIMATIC LAD, STL, and
FBD
Network 1
LD
On the first scan,
enable State 1. S
Beginning of State 1
Network 2
control region
LSCR
Network 3
Turn on the red light on
LD
First Street.
S
R
TON
Turn off the yellow and
green lights on First
Street.
Start a 2-second timer.
Network 4
Transition to State 2
LD
after a 2-second delay.
SCRT
Network 5
End of SCR region for
SCRE
State 1
SIMATIC Instructions
STL
SM0.1
S0.1, 1
S0.1
SM0.0
Q0.4, 1
Q0.5, 2
T37, 20
T37
S0.2
9-159