At a Glance

The attributes of a data instance are its defining information.

This information is:

  • its name (except for the direct addressing data instances)

  • its topological address (except for unlocated data type instances)

  • its data type, which can belong to one of the following families:

    • Elementary Data Type (EDT)

    • Derived Data Type (DDT)

    • Device derived Data type (Device DDT)

    • Function Block data type (EFB\DFB)

    • Sequential Function Chart data type (SFC)

  • an optional descriptive comment (1024 characters maximum). Authorized characters correspond to the ASCII codes 32 to 255

Name of a Data Instance

This is a symbol (32 characters maximum) automatically instantiated with a defaut name. This name can be modified by the user.

Certain names cannot be used, for example:

  • key words used in text languages

  • names of program sections

  • names of data types that are predefined or chosen by the user (structures, tables)

  • names of DFB/EFB data types that are predefined or chosen by the user

  • names of Elementary Functions (EF) that are predefined or chosen by the user

Names of Instances Belonging to the SFC Family

The names of instances are declared implicitly while the user drafts his sequential function chart. They are default names supplied by the manufacturer which the user can modify.

Manufacturer-supplied default names:

SFC object

Name

Step

S_<section name>_<step No.>

Step of Macro step

S_<section name>_<macro step No.>_<step No.>

Macro step

MS_<section name>_<step No.>

Nested macro step

MS_<section name>_<macro step No.>_<step No.>

Input step of Macro step

S_IN<section name>_<macro step No.>

Output step of Macro step

S_OUT<section name>_<macro step No.>

Transition

T_<section name>_<transition No.>

Transition of Macro step

T_<section name>_<macro step No.>_<transition No.>

Names of Instances Belonging to the Function Block Family

Instance names are implicitly declared while the user inserts the instances into the sections of the application program. They are default names supplied by the manufacturer which the user may modify.

Syntax of manufacturer-supplied default names:

NOTE: Instance names do not include the name of the section in which the instance is used, since it can be used in different sections of the application.

Access to an Element of a DDT Family Instance

The access syntax is as follows:

Rule:

The maximum size of the access syntax is 1024 characters, and the possible limits of a derived data type are as follows:

  • 10 nesting levels (tables/structures)

  • 6 dimensions per table

  • 4 digits (figures) to define the index of a table element

Access to an Element of a Device DDT Family Instance

The access syntax is as follows:

Rule:

The maximum size of the access syntax is 1024 characters, and the possible limits of a derived data type are as follows:

  • 10 nesting levels (tables/structures)

  • 6 dimensions per table

  • 4 digits (figures) to define the index of a table element