Latching Relay - Siemens LOGO! Manual

4.4.21

Latching relay

Short description
Input S sets output Q, input R resets output Q again.
Symbol in LOGO!
Timing diagram
Switching response
A latching relay represents a simple binary element. The output value depends on the status
at the inputs and on the previous output status. The following table shows the logic once
again:
S
n
0
0
1
1
When retentivity is enabled, the current status of the output signal is retained after a power
failure.
LOGO!
Manual, 10/2017, A5E01248535-AA
Wiring
Input S
Input R
Parameter
Output Q
R Q Comment
n
0 x The status is retentive
1 0 Reset
0 1 Set
1 0 Reset (takes priority over Set)
4.4 Special functions list - SF
Description
You set output Q with a signal at input S.
You reset output Q with a signal at input R. If S and R
= 1, the output is reset.
Retentivity:
/ = No retentivity
R = The status is retentive.
Q is set with a signal at input S, and reset with a
signal at input R.
LOGO! functions
175