Hi folks….. I have question about functions in s300. Function are procedures that do not save data so I can use only temp variables in local data stack. So if I have function and I call it twice for example does cpu reserve different local data for the second instance of the function. Im asking that because I have this situation. I have function and in I set a bit (temp var)in it and on the next instance this bit is already set …. Is that mean that function safe the state of temp vars ?

Hello fury_omen

For FC’s you cannot use TEMP’s to store data, the option for you will be FB’s with Instance DB, where you can declare STAT  statics variables.

The following link Difference ...   explains weell the differences between FC's and FB's
Regards
Marciano

Let look that example. I have two function. The first ‘fc4’ called the second ‘fc3’ twice. In ‘fc3’ I have set coil ‘temp1’. The output of ‘fc3’ depends on two inputs var ‘in1’ and ‘in2’ and local var ‘temp1’. On second instance of function ‘fc3’ I have only to set ‘in1’ and the output ‘pass’ is on. The ‘temp1’ var is set in the second instance on function ‘fc3’. Is what mean that local data is saved? I just copied these function in STL just past them in stap7 and turn the view to LAD and test it will PLCSim. So my question is if I set tamp var  in function how to know what happen with this var in second instance of this function is it will be clear, set or undefined   

fc 3

in: in1 – bool; in2 – bool;

out: out1 – bool

temp: temp1 – bool

A     #in1

S     #temp1

A     #in2

A     #temp1

=     #out1

fc4

in: n1 - bool; n2 - bool

out: pass – bool

temp:  t1 – bool; t2 – bool

A     M     10.1

=     L      1.0

BLD   103

A     M     10.2

=     L      1.1

BLD   103

A     #n1

JNB   _001

CALL  FC     3

in1 :=L1.0

in2 :=L1.1

out1:=#t1

_001: NOP   0

A     M     10.3

=     L      1.0

BLD   103

A     M     10.4

=     L      1.1

BLD   103

A     #n2

JNB   _002

CALL  FC     3

in1 :=L1.0

in2 :=L1.1

out1:=#t2

_002: NOP   0

A     #t1

AN    #t2

=     #pass

ob1

A     M     20.0

=     L     21.0

BLD   103

A     M     20.1

=     L     21.1

BLD   103

A     M      1.0

JNB   _001

CALL  FC     4

n1  :=L21.0

n2  :=L21.1

pass:=M30.0

_001: NOP   0

You should see the TEMP as a sketch or draft , temporarily variables valid inside the block only.
Now answering your question, they are not cleared, actually they ” keep the state”., and not officially if your program have only one OB and one FC you could have your TEMP’s holding values… However because this area is shared with other blocks with same priority, the TEMP area will be constantly been updated /several updates during one single scan – so I think you can say the result would be undefined.

Yep, my mistake is ‘in2’.

So in one OB, I do NOT have fresh instance on same function if I call it more than ones. And this happed because the local date stack is not cleared after end of function.  If I want everything to be fresh I have to clear all set bit and so on before exit from function. Is that right ?