When to use a formal call? When to use a non-formal call?
To brush up your knowledge:
Example for a formal call: Inst2 (EN := TRUE,IN1:=10,IN2 := 20,T1 := T#3ms, OUT => result); Example for a non-formal call: Inst2 (10,20,T#3ms)
See " Call of function block instance in ST ", " Call of function in ST " and/or " Call of method in ST " , if you need more details on formal and non-formal call.
Now to the answer when to use formal call vs. non-formal call: Certainly you will be faster to enter a non-formal call than a formal call. However, the usage rather depends on the decision which parameters you want/must enter within the call.
The following table should make this decision easier as it lists which call is suited for which purpose (= icon 
) and which call is not suited (= icon 
). The table also lists conditions that require just one of the calls (= icon
).
|
Purpose |
Formal call |
Non-formal call |
|
The call should not list all →input variables or →output variables. |
|
|
|
The call should list all input variables. |
|
|
|
The call should list EN/ENO. |
|
|
|
The call should list assignments of output variables. |
|
|
|
The call should list variables in any order. |
|
|
|
A function block instance should be assigned as parameter to the called function block instance or function and it should be called there. |
|
|
|
Condition |
Formal call |
Non-formal call |
|
In-out variables are declared in the called function block or function. |
|
|
logi.cals
recommends to install and use the most current versions of
logi.CAD 3
and the runtime system so that the latest features and problem fixes
according to the
release notes are provided in the used version.
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