User manual

48 Publication LOGIX-AP010B-EN-P - May 2010
Chapter 2 Software Conversions - Program Structure
Programming Languages
This section describes the programming languages that are available with
Step 5 and RSLogix 5000 software. All languages are not standard and
depends on the version of the software purchased. Selection of the
RSLogix 5000 language most suitable to the task will result in easier program
design, more rapid coding, and a program that is easier to understand.
There is one significant difference between the Step 5 and RSLogix 5000
languages. In Step 5, Statement List is the native language of the controller.
This means that other languages are translated to STL. In RSLogix 5000
software, all the languages are native languages in the controller so each is
compiled without reference to any of the others.
Step 5 has these three standard languages:
• Statement List (STL) - is a text-based programming language that uses
statements to define what to execute. In German it is referred to as
Anweisungsliste (AWL). A similar format, called Structured Text, exists
in RSLogix 5000 software.
• Ladder Diagram (LAD) - is a programming method using graphic
symbols in a schematic circuit diagram format. In German it is referred
to as Kontaktplan (KOP).
• Control System Flowcharts (CFS) - is a programming method using
graphic symbols. In German it is referred to as Funktionsplan (FUP).
This format also exists in RSLogix 5000 software and is referred to as
Function Block Diagram.
GRAPH 5 is an extension of Step 5 and a software package for graphical
programming of sequential control systems. GRAPH 5 allows a sequence to
be programmed by breaking it down into a series of steps and transitions,
which are then programmed by using one of the standard languages (STL,
LAD or CFS).
RSLogix 5000 software has four programming languages:
• Ladder Diagram (LD) – comparable to Step 5 LAD, with an expanded
instruction set.
• Structured Text (ST) – comparable in structure to higher level computer
languages such as C and VBA.
• Function Block Diagram (FBD) – Equivalent to Step 5 CFS.
• Sequential Function Chart (SFC) – comparable to Step 5 GRAPH 5/II.
When converting an application from S5 to Logix it is not necessary to choose
the same language in RSLogix 5000 software as was used in Step 5.