Principle

In Instruction List, a user function block is called by a CAL instruction, followed by the name of the DFB instance as an operand and a list of arguments (optional). Arguments are displayed in the list between brackets and separated by commas.

In Instruction List, there are three possible ways of calling a DFB:

• The instruction CAL DFB_Name is followed by a list of arguments that are assignments (parameter = value). In this case, the order in which the arguments are entered in the list is not important.

  The EN input parameter can be used to control the execution of the function block.

• The instruction CAL DFB_Name is followed by a list of arguments that are values (expression, object or immediate value). In this case, the order in which the arguments are entered in the list must follow the order of the DFB input parameters, including for non-assigned inputs (the argument is an empty field).

  It is not possible to use EN and ENO parameters.

• The instruction CAL DFB_Name is not followed by a list of arguments. In this case, this instruction must be preceded by the assignment of the input parameters, via a register: loading of the value (Load) then assignment to the input parameter (Store). The order of assignment of the parameters (LD/ST) is not important; however, you must assign all the required input parameters before executing the CAL command. It is not possible to use EN and ENO parameters.

CAL DFB_Name (argument 1,argument 2,...,argument n)

or

LD Value 1

ST Parameter 1

...

LD Value n

ST Parameter n

CAL DFB_Name

Use of EN\ENO Parameters

See EN and ENO Parameters.

Example of a DFB

The following example explains the different calls of a DFB in Instruction List. This is the instance Cpt_1 of the Cpt_parts: type DFB

DFB Call when the Arguments Are Assignments

When the arguments are assignments, the DFB call Cpt_1 is performed with the following syntax:

CAL Cpt_1 (Reset:=Clear, Presel:=%MD10, Count:=100, Done=>%Q1.2.1)

Where the input parameters assigned by a value (expression, object or immediate value) are entered in the list of arguments, the syntax is:

CAL Cpt_1 (Reset:=Clear, Presel:=%MD10, Count:=100)

...

LD Cpt_1.Done

ST %Q1.2.1

In order to make your application program more legible, you can enter a carriage return after the commas that separate the arguments. The sequence then takes the following syntax:

CAL Cpt_1(

Reset:=Clear,

Presel:=%MD10,

Count:=100,

Done=>%Q1.2.1)

Elements of the DFB Call Program

The following table lists the different elements of the DFB call program.

DFB Call when the Arguments Are Values

When the arguments are values, the DFB call Cpt_1 is performed with the following syntax:

CAL Cpt_1 (Clear, %MD10,, 100)

...

LD Cpt_1.Done

ST %Q1.2.1

Elements of the DFB Call Program

The following table lists the different elements of the DFB call program.

DFB Call with no Argument

When there is no argument, the DFB call Cpt_1 is performed with the following syntax:

LD Clear

ST Cpt_1.Reset

LD %MD10

ST Cpt_1.Presel

LD 100

ST Cpt_1.Count

CAL Cpt_1(

...

LD Cpt_1.Done

ST %Q1.2.1

Elements of the DFB Call Program

The following table lists the different elements of the DFB call program.