Siemens SIMATIC S5 Manual page 105

S5-115F Manual
RS flip-flop with flags
A "1" at input I 2.6 sets flip-flop F 11.7 (signal state "1").
If the signal state at input I 2.6 changes to "0", the state of
flag F 11.7 is maintained, i.e., the signal is latched.
A "1" at input I 1.3 resets the flip-flop (signal state "0"). If
the signal state at input I 1.3 changes to "0", flag F 11.7
maintains signal state "0".
The signal state of the flag is scanned and transferred to
output Q 3.4.
STL
A I 2.6
S F 11.7
A I 1.3
R F 11.7
A F 11.7
= Q 3.4
EWA 4NEB 811 6149-02
Example
CSF
F 11.7
I 2.6 S
R Q
I 1.3 Q 3.4
STEP 5 Operations
Circuit Diagram
I 1.3 I 2.6
F 11.7
LAD
F 11.7
I 2.6
S
I 1.3
R Q
Q 3.4
3-9