Siemens LOGO! - Latching Relay; Switching Response

LOGO! Manual
A5E00380835-01
198
4.4.21 Latching relay
Short description
Input S sets output Q, input R resets output Q again.
Symbol in
LOGO!
Wiring Description
Input S You set output Q with a sig-
nal at input S.
Input R You reset output Q with a
signal at input R. If S and
R = 1, the output is reset.
Parameter Retentivity:
/ = No retentivity
R = The status is retentive.
Output Q Q is set with a signal at in-
put S, and reset with a sig-
nal at input R.
Timing diagram
S
R
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
R
n
Q
Comment
0 0 x The status is retentive
0 10Reset
1 01Set
1 1 0 Reset (takes priority over Set)
When retentivity is enabled, the current status of the output
signal is retained after a power failure.
LOGO! functions