Iec 61131-3 Second edition 2003-01 Programmable controllers – Part 3: Programming languages

Table 19 - Graphical negation of Boolean signals
No.
Feature
a, b
Representation
1
Negated input
+---+
---O| |---
+---+
2
Negated output
+---+
----| |O---
+---+
a 
If either of these features is supported for functions, it shall also
be supported for function blocks as defined in 2.5.2, and vice
versa.
b 
The use of these constructs is forbidden for in-out variables.
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– 48 –
61131-3 
 IEC:2003(E)
Figure 5 illustrates both the graphical and equivalent textual use of functions, including the use of a
standard function (ADD) with no defined formal argument names; a standard function (SHL) with
defined formal argument names; the same function with additional use of EN input and negated ENO
output; and a user-defined function (INC) with defined formal argument names.
Example
Explanation
+-----+
| ADD |
B---| |---A
C---| |
D---| |
+-----+
Graphical use of ADD function
(See 2.5.1.5.2)
(FBD language; see 4.3)
(No formal variable names)
A := ADD(B,C,D);
Textual use of ADD function
(ST language; see 3.3)
+-----+
| SHL |
B---|IN |---A
C---|N |
+-----+
Graphical use of SHL function
(See 2.5.1.5.3)
(FBD language; see 4.3)
(Formal argument names)
A 
:=
SHL
(
IN
:=
B
,
N
:=
C
);
Textual use of SHL function
(ST language; see 3.3)
+---------+
| SHL |
ENABLE---|EN ENO|O--NO_ERR
B---|IN |---A
C---|N |
+---------+
Graphical use of SHL function
(See 2.5.1.5.3)
(FBD language; see 4.3)
(Formal argument names; use of EN input
and negated ENO output)
A 
:=
SHL
(EN:=ENABLE, 
IN:=B
, 
N:=C,
NOT ENO => NO_ERR
);
Textual use of SHL function
(ST language; see 3.3)
+-----+
| INC |
| |---A
X---|V---V|---X
+-----+
Graphical use of user-defined
INC function
(FBD language, see 4.3)
(Formal argument names for VAR_IN_OUT)
A := INC(V := X) ;
Textual use of INC function
(ST language, see 3.3)