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

Table 53 - Function block invocation and
Function invocation features for IL language
No.
DESCRIPTION/EXAMPLE
1a
CAL of function block with non-formal argument list:
CAL C10(%IX10, FALSE, A, OUT, B)
CAL CMD_TMR(%IX5, T#300ms, OUT, ELAPSED)
1b
CAL of function block with formal argument list:
CAL C10(
CU := %IX10,
Q => OUT)
CAL CMD_TMR(
IN := %IX5,
PT := T#300ms,
Q => OUT,
ET => ELAPSED,
ENO => ERR)
2
CAL of function block with load/store of arguments (note 2)
LD
A
ADD
5
ST
C10.PV
LD
%IX10
ST
C10.CU
CAL
C10
3
Use of function block input operators:
LD
A
ADD
5
PV
C10
LD
%IX10
CU
C10
4
Function invocation with formal argument list:
LIMIT(
EN:= COND,
IN:= B,
MN:= 1,
MX:= 5,
ENO=> TEMPL
)
ST A
5
Function invocation with non-formal argument list:
LD 1
LIMIT B, 5
ST A
Copyright International Electrotechnical Commission 
Provided by IHS under license with IEC
Not for Resale
No reproduction or networking permitted without license from IHS
--``````-`-`,,`,,`,`,,`---

---

– 128 –
61131-3 
 IEC:2003(E)
Table 53 - Function block invocation and
Function invocation features for IL language
No.
DESCRIPTION/EXAMPLE
NOTE 1 A declaration such as
VAR
C10 : CTU;
CMD_TMR : TON;
A, B : INT;
ELAPSED : TIME;
OUT, ERR, TEMPL, COND : BOOL;
END_VAR
is assumed in the above examples.
NOTE 2
This usage is an exception to the rule given in 2.5.2.1
that “The assignment of a value to the inputs of a function
block is permitted only as part of the invocation of the
function block.”
The input operators shown in table 54 can be used in conjunction with feature 3 of table 53. This
method of invocation is equivalent to a CAL with an argument list, which contains only one variable
with the name of the input operator. Arguments, which are not supplied, are taken from the last
assignment or, if not present, from initialization. This feature supports problem situations, where
events are predictable and therefore only one variable can change from one call to the next.
EXAMPLE 1
Together with the declaration
VAR C10: CTU; END_VAR
the instruction sequence
LD
15
PV
C10
gives the same result as
CAL
C10(PV:=15)
The missing inputs R and CU have values previously assigned to them. Since the CU input
detects a rising edge, only the PV input value will be set by this call; counting cannot
happen because an unsupplied argument cannot change. In contrast to this, the
sequence
LD
%IX10
CU
C10
results in counting at maximum in every second call, depending on the change rate of the
input %IX10. Every call uses the previously set values for PV and R.
EXAMPLE 2
With bistable function blocks, taking a declaration
VAR FORWARD: SR; END_VAR
this results into an implicit conditional behavior. The sequence
LD
FALSE
S1
FORWARD
does not change the state of the bistable FORWARD. A following sequence
LD
TRUE
R
FORWARD
resets the bistable.
Copyright International Electrotechnical Commission 
Provided by IHS under license with IEC
Not for Resale
No reproduction or networking permitted without license from IHS
--``````-`-`,,`,,`,`,,`---

---

61131-3 
 IEC:2003(E)
– 129 –