====== Simatic TIA Portal know-how ======
I predict that in the chapter, I will write the descriptions in my own words, as if I were trying to explain things to a friend. The description may not be professional this way, but my goal is for anyone who reads to understand what is described.

===== FC / FB description =====

==== FC: function ====
{{anchor:fc}}

FCs are programming blocks that do not require static variables, that is, they do not need internal information that would be stored from one cycle to another. It is therefore not necessary to assign data blocks, i.e. DBs, to FCs. 

In the references, I denote FCs as follows: <color white/yellow>[[de:s7:tia_knowhow#fc|_FC_]]</color> 

for example: <color white/yellow>[[de:s7:tia_knowhow#fc|_FC_]]</color>  <color green>Result</color> := **ABS** (<color blue>Value</color>);

<WRAP center round important 80%>
I repeat because it is important: The internal variables of the FC are valid only within one cycle, they lose their values for the next cycle. If you need to store information, use the FB or call DB, merkel.
</WRAP>


=== Add new FC ===
{{:de:s7:add_new_fc.png|Add new FC}}

  * double click to "Add new block"
  * chose "Function"
  * type a new name

==== FB: function blocks ====
FBs are a bit more complex modules than FCs. FBs are able to define cyclical variables, these are "static" variables. These are not actually stored in the FB, but will be assigned a datablock (DB) to each FB and it will store these variables. These DBs should be called IDBs (instant datablocks) because, unlike global DBs, they are assigned to a specific FB. In addition to storing variables, IDBs are also suitable for storing embedded FBs, this will be discussed later. The IDB will be assigned to a given SC during the first call.

In the references, I denote FBs as follows: <color white/orange>[[de:s7:tia_knowhow#fc|_FB_]]</color> 

for example: <color white/orange>[[de:s7:tia_knowhow#fc|_FB_]]</color>  
<color green>RetVal</color> ([[de:s7:tia_datatypes#int|INT]]):= BLKMOV
(<color blue>SRCBLK :=</color> source block ([[de:s7:tia_datatypes#variant|VARIANT]]);
<color blue>DSTBLK =></color> destination block ([[de:s7:tia_datatypes#variant|VARIANT]]);
<color red>ENO</color> => operation enable 
); 

=== Add new FB ===
{{:de:s7:add_new_fb.png|Add new FB}}

  * double click to "Add new block"
  * chose "Function block"
  * type a new name

==== FC / FB variable types ====
When we open the newly created Fc or FB (FB in the example) we will see the following image:

{{:de:s7:fc_fb_var_types.png|FC / FB variable types}}

Field reports:
^Name^FC / FB^description|
|**Input**| FC and FB |Variables read by modules.|
|**Output**| FC and FB |Variables write by modules.|
|**InOut**| FC and FB |Variables read and then written back by modules. Changes made to the module are reflected in the outputs.|
|**Static**| FB only |static variables: their value is retained because they are stored in the IDB assigned to the FB. If you open the IDB, you can follow the change in the value of the variables there.|
|**Temp**| FC and FB |Temporary variables: they can only be used within the given cycle, they will lose their value at the time of another call.|
|**Constant**| FC and FB |Constant values: their value must not change.|
|**Return**| FC only |the return value of the function, which is the name of the function. In the case of an external call: \\ retval: = Function_name ();|

==== Call FCs ====
Calling FCs is easier:
  - the part of the program (FC, FB or OB) from which the FC is to be called must be opened.
  - drag-and-drop the FC from the **"instructions"** window, or simply plug it in. For example, after indentation, "LN" FC looks like this: //LN (_real_in_)//
  - you need to know, for example [[de:s7:scl_reference_math#ln|from here]] that the "LN" FC is calling floating-point numbers, ie REAL or LREAL.
  - the return value must also be given, eg: out:= LN(in); where in and out are REAL.

==== Call FBs ====
{{anchor:call_fb}}
When calling FBs, we have two options:
  - each invited sub_FB receives its own IDB
  - sub_FBs are treated as an embedded function and their data area will be "taped" to the IDB of the calling FB.

{{:de:s7:fb_call_1.png|Call FB 2 methods}}

Let's see this through examples, let's take one of the most commonly used methods, TON:

First method, call with separate IDBs:
|< 100% 65% 35% >|
|{{ :de:s7:fb_call_2.png |}}|Using two TON FBs, both calling their own IDBs|
|{{:de:s7:fb_call_3.png|}}|Content of one of the IDBs|

Second method, call embedded FBs:
|< 100% 65% 35% >|
|{{:de:s7:fb_call_4.png|}}|In the case of embedding, the functions must be called from the "static" block of the calling FB (just type "TON" for the "data type". FBs must be called in the program in much the same way, of course the DB call must be omitted.|
|{{:de:s7:fb_call_5.png|}}|The image shows the data of the embedded FBs in the IDB of the calling FB. The great advantage of this method is that the program is easy to import / export / copy, as you only need one FB definition.|

===== Switch off "optimization" attribute of DBs =====
{{anchor:db_opt}}
By default, the TIA portal turns **on** the //"optimization"// attribute of DBs, which means that the order of variables in DBs is automatically optimized. 

In many cases, this causes serious problems when the given variables have to remain in predefined positions, such as OPC, or typically any similar communication (Modbus, PN, ..) DB. For example, the [[de:s7:scl_reference#blkmov|BLKMOV]] command does not work with optimized DBs either. 

To deactivate, right-click on the DB and select **Properties...** and then **Attributes**:

{{:de:s7:opt_db_out.png|The "optimization" attribute of DBs}}

The **"optimized block access"** attribute in the menu must be turned **off**.

For generated DBs, the //{S7_Optimized_Access: = 'TRUE'}// entry should be modified as follows: **{S7_Optimized_Access: = 'FALSE'}**.

===== Import source code to the TIA portal =====
{{anchor:import}}

| 1: Double click to: "**Add new external file**" by "**External source files**" menu \\ 2: Choose files and open|{{:de:s7:import_1.png|Import source code to the TIA portal}}|
| 3: right click to the file \\ 4: choose "**Generate blocks from file**" \\ 5: IF the message "**blocks can be overwriten**" comming: press OK. \\ 6: Enjoy the code! Think about how much energy and money you have saved yourself, throw me some coin [[de:s7:tia_knowhow#donate|for a coffee through Paypal!]]|{{:de:s7:import_2.png|Import source code to the TIA portal}}|

==== End of site ====
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