Nand; Nor - Siemens LOGO! Series Manual

Programming LOGO!

3.4.4 NAND

The parallel connection of a num-
ber of normally closed contacts is
represented in a circuit diagram as
follows:
The block is called NAND because its output (Q) only has the state 0 if I1
and I2 and I3 have the state 1 (i.e. are closed).
Logic table for NAND
I1 I2 I3
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1

3.4.5 NOR

The series connection of a number
of normally closed contacts is rep-
resented in a circuit diagram as
follows:
The output of the NOR block is only switched on (state 1) when all the
inputs are switched off (state 0). As soon as any of the inputs is switched
on (state 1), the output is switched off.
20
In LOGO! this is a NAND block.
The symbol for it is as follows:
Q
1
1
1
1
1
The following applies to NAND: x = 1
1
(x means the input is not used)
1
0
In LOGO! this is a NOR block. The
symbol for NOR is as follows:
I1
I2 Q
I3
I1
I2
Q
I3
LOGO! manual
EWA 4NEB 712 6006-02