Latching Relay; Switching Response - Siemens Logo! Manual

LOGO! functions

4.4.21 Latching relay

Short description
Input S sets output Q, input R resets output Q again.
Symbol in
LOGO!
Timing diagram
R
S
Q

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.
198
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)
Description
You set output Q with a sig-
nal 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 in-
put S, and reset with a sig-
nal at input R.
LOGO! Manual
A5E00380835-01