P877
IEC 61131 standardises the programming language, the instruction sets and the handling and structuring of projects. As standard the IEC61131 capability is included on every MC464 controller in a limited form.
To unlock this functionality fully you will need a ‘feature enable code’
IEC-defined programming languages
IEC 61131-3 describes three graphical and two textual programming languages and defines their language elements as well as their syntax.
Ladder Diagram (LD)
The Ladder Diagram language (LD) has been used since the invention of PLCs for their programming. LD is suited to programming sequential logic and for this reason is accepted worldwide and can be used universally. Development engineers as well as service engineers are capable to analyze the LD programming of a controller on site and diagnose and troubleshoot problems if required. IEC 61131-3 defines a complete LD set of instructions, consisting of different types of contacts and coils
Contacts lead (according to their type) the power from the left to the right. Coils store the incoming value. Both, contacts and coils, are assigned to Boolean variables. An LD network can be supplemented by jumps, returns, labels and comments
In addition, you can use FBD elements in LD networks, as shown in the following example
Function Block Diagram (FBD
The language Function Block Diagram (FBD) defined in IEC 61131-3 consists of different functions and function blocks that are either linked or connected to variables. In FBD networks, jumps, labels and returns can be used. Apart from standalone use of FBD, LD elements can be connected to timers, counters and type converters etc
Programming is similar to the creation of functional diagrams or block diagrams, with the control logic being created by simply connecting blocks and elements.
FBD is frequently used in the process industry due to the flow-oriented properties of function blocks (reading FB inputs, processing, setting FB outputs).
Instruction List (IL)
The Instruction List language (IL) is a textual programming language and is similar to the assembler language. Code in IL consists of a sequence of instructions separated by lines, which consist of one operator ("command"), one operand (variable, constant or instance name) and one optional modifier respectively. Jumps and labels can be used.
The Edit Wizard is responsible for syntactically correct insertion of the language constructions. Furthermore, the text editor simplifies the programming work through syntax highlighting (colour marking of language elements). IL is mainly used if the processing speed of the PLC program has high priority.
Structured Text (ST)
The textual Structured Text language (ST) is similar to the high-level language PASCAL or BASIC and is used for this reason by numerous programmers. ST uses statements like IF...THEN or FOR...NEXT. The Edit Wizard is responsible for syntactically correct insertion of the language constructions. Furthermore, the text editor simplifies the programming work through syntax highlighting (colour marking of language elements).
The syntax and the set of instructions of ST are optimally suited for mathematical calculations and data manipulations. In connection with arrays and structures supported by MULTIPROG®, the programmer thus has very flexible and powerful possibilities.
Sequential Function Chart (SFC)
SFC is a status-oriented language. The code body programmed in the graphic language SFC consists of steps and transitions. A step contains the logic for a certain machine status, a transition represents a condition under which processing of the code is continued with the next step. SFC is particularly suited to applications that can be structured into clearly identifiable steps.
The logic contained in a step can be programmed in any other IEC programming language, adjusted to the conditions of the respective machine status. This way, SFC becomes the first choice particularly for commissioning and the debug phase, as the structuring of the application into single steps significantly simplifies program diagnosis in case of errors - especially compared to a typical LD program with a large number of networks.
As standard Trio provides support for LD and ST, however programming interface for other IEC61131-3 languages can be purchased.
The MC464 will be provided with a library of Motion Instructions for use with the IEC61131 programming tools. These libraries will allow you to access the normal Trio set of motion instructions.
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