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C 1.9)
Programming
of logic sequences
The logic-commands
of -the PLC can be arranged
in chains to form a logic seqluence.
Logic sequences
are interrupted
by the PLC-commands:
I?, RN, S, SN or =; a new logic sequence
begins after
these commands.
C 1.9.1)
Logic sequences
with
U-commands
A logic sequence
with
U--commands
effects
a series switching
of contacts.
These contacts
are normally
open.
This corresponds
to an AND-gate.
PLC-Programme
Gating-logic
U El
U E2
= Al
Al
Examples:
a)
The lamp Ll is connected
to the output
43. The
closing of the contacts
Sl should
result
In the
illumination
of the lamp. The contacts
are
connected
to input
E27 of the PLC.
PLC-Programme:
U E2'7
= A413
This PLC-programme
efflects the following
switching:
) +24V
I
51
C
i
Ll
Abbreviated
Symbol
El
E2
Al
b)
Truth
table
El
E2
Contact
0
-0
0
1
1
0
1
1
f
\ El
E2
A
1
t
+ 24V
The relay Kl should energise, in the event of the
contalzts Sl, S2 and S3 closing simultaneously.
PLC-F'rogramme:
U E28
U E29
U E30
= A44
The PLC-programme effects a series switching of the
contalzts Sl , S2 and S3:
t
+24V
\I
Sl
18
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