General

The code section(s) define(s) the process the DFB is to carry out, as a function of the declared parameters.

A DFB may contain several code sections; the number of sections being unlimited.

Programming Languages

To program DFB sections, you can use the following languages:

  • Instruction List (IL)

  • Structured Text (ST)

  • Ladder language (LD)

  • Functional Block Diagram (FBD)

Defining a Section

A section is defined by:

  • a symbolic name that identifies the section (maximum of 32 characters)

  • a validation condition that defines the execution of the section

  • a comment (maximum of 256 characters)

  • a protection attribute (no protection, write-protected section, read/write-protected section)

Programming Rules

When executed, a DFB section can only use the parameters you have defined for the function block (input, output and input/output parameters and internal variables).

Consequently, a DFB function block cannot use either the global variables of the application, or the input/output objects, except the system words and bits (%Si, %SWi and %SDi).

A DFB section has maximum access rights (read and write) for its parameters.

Example of Code

The following program provides an example of Structured Text code