Flip-Flop Blocks - Siemens SIMATIC S7 F Manual

Fail-Safe Blocks
Error Information in Diagnostic Buffer
Error Code (W#16#...)
0x75D9
0x75DA
8.9

Flip-Flop Blocks

Block
F_RS_FF
F_SR_FF
8.9.1 F_RS_FF
Function
The block executes the function of an RS flipflop (resetting dominant).
The RS flipflop is reset if the signal state at the input R = 1 and at the input S =
0. The flipflop is set if the input R = 0 and the input S = 1. If the result of the logic
operation is 1 at both inputs, the flipflop is reset.
Truth Table
R S
0 0
0 1
1 0
1 1
I/Os
Name
Inputs: R
S
Outputs: Q
QN
8-100
Description
Invalid REAL number
Error in the safety data format (error due to online modification of the
Safety Program or internal CPU fault)
Description
RS flipflop, resetting dominant
SR flipflop, setting dominant
QN QNn
Qn-1 QNn-1
1 0
0 1
0 1
Data Type Explanation
F_BOOL Reset
F_BOOL Set
F_BOOL Output
F_BOOL Negating output
Default
0
0
0
1
Fail-Safe Systems
A5E00085588-03