Rockwell Automation Logix5000 Controllers IEC 61131-3 Compliance Programming Manual - Manual (Page 11)

Rockwell Automation Publication 1756-PM018C-EN-P - November 2012 11
IEC61131-3 Compliance Chapter 1
Programming Languages The IEC61131-3 specification defines five (5) different programming languages
and a set of common elements. All languages are defined as optional but at least
one must be supported in order to claim compliance with the specification. The
IEC61131-3 programming language components are defined as follows:
• Common Language Elements
• Common Graphical Elements
• Instruction List (IL) Language Elements
• Structured Text Language (ST) Elements
• Ladder Diagram (LD) Language Elements
• Sequential Function Chart (SFC) Language Elements
• Function Block Diagram (FBD) Language Elements
Logix5000 controllers and the Logix Designer application provide support for
the common language elements and the Structured Text, Ladder Diagram,
Sequential Function Chart, and Function Block Diagram language options.
Additionally, the environment utilizes an ASCII import/export format based on
the Structured Text language. The instruction set and program file exchange
features are discussed in detail in the sections that follow.
Instruction Set The instruction set specified by IEC61131-3 is entirely optional. The
specification lists a limited set of instructions that if implemented must conform
to the stated execution and visual representation. IEC61131-3 however, does not
limit the instructions set to those listed within the specification. Each PLC
vendor is free to implement additional functionality in the form of instructions
over and above those listed by the specification. Examples of such extended
instructions are those needed to perform diagnostics, PID loop control, motion
control and data file manipulation. Because extended instructions are not defined
by the IEC61131-3 specification, there is no guarantee that the implementation
between different PLC vendors will be compatible. Thus utilization of these
instructions may preclude the movement of logic between vendors.
Logix5000 controllers and the Logix Designer application provide a suite of
instructions that execute as defined by the IEC61131-3 specification. The
physical representation of these instructions maintain their look and feel with
existing systems so as to reduce the training cost associated with working with the
environment. In addition to the IEC61131-3 compliant instructions, a full range
of instructions from existing products have been brought forward into the
environment so that no functionality is lost.