LANGUAGES FOR PLC PROVRAMMING

What are PLC programming languages?


The PLC programming languages are symbols, characters, and rules of use that were designed to allow users to communicate with the machines. Thanks to this link, we can be able to create a program with instructions to control the operation of any process or machine. PLC Communication between two or more PLC’s Communication between two or more PLCs happens through a special connection based on rules, which allow the transfer of data or information between each of these. These types of rules are known as «communication protocol», some of these are Profibus, Fieldbus, Modbus, Devicenet, Interbuss, among some others. Communication protocol Types of PLC programming languages There is diversity within programming languages because users have different training in different branches of engineering, for example, electrical and electronic engineers or technicians are used to using symbols in electrical diagrams, while systems engineers always use written languages, for which some prefer to program a more visual language and others prefer a written language. PLC programming languages can be classified into two classes, high and low-level languages each with different types. High-level languages In this category are the languages that are graphic, since they use a symbol interface to declare the control instructions, one of the disadvantages of these visual languages is that the programming is limited to the symbols that are provided. Ladder or ladder diagram This language was one of the pioneers since it was one of the first to be used since it closely resembles diagrams with relays. It is called ladder because it is very similar to the structure of a ladder since it contains two vertical rails, and several horizontal rails (in this case they would be the steps). Main features: The 2 vertical rails are power (in the case of VCD one is voltage and the other is ground and in VCA they are L1 and L2) Instructions are placed on the left side The exits are always placed on the right side. Multiple instructions or multiple outputs can be placed in parallel. The plc processor interprets the data from top to bottom and from left to right. Ladder Blocks diagram Logical symbol blocks are used in this type of programming. The outputs are not required to be incorporated into an output coil, because the output is assigned at the outputs of the logic blocks. These diagrams are mostly preferred by people accustomed to working with logic gate circuits since the symbology used is equivalent. Main features: The outputs of the blocks will not be connected to each other. The evaluation of a network is finished before starting the next Blocks diagram Block diagram Low-level languages In this type are the programming languages through text, using character strings to indicate the control instructions. Instruction list This type of language is the oldest and is the basis for all the programming languages that exist, this language is the precursor of the ladder diagram since it was used when computers did not yet have the graphical capacity. All languages are translated into instructions list. Main features: All languages can be translated to the instruction list, but not vice versa. Programming is more compact. This language is the most complete of all. Instruction list Structured text The structured text is made up of a series of instructions that can be carried out, as is the case with higher languages, on a conditional basis. This language is very similar to the C language and especially to PASCAL (“IF..THEN..ELSE”) or in sequential loops (WHILE..DO). Main features: Treats uppercase and lowercase letters interchangeably Supports complex arithmetic instructions.What are PLC programming languages? The PLC programming languages are symbols, characters, and rules of use that were designed to allow users to communicate with the machines. Thanks to this link, we can be able to create a program with instructions to control the operation of any process or machine. PLC Communication between two or more PLCs Communication between two or more PLCs happens through a special connection based on rules, which allow the transfer of data or information between each of these. These types of rules are known as «communication protocol» , some of these are Profibus, Fieldbus, Modbus, Devicenet, Interbuss, among some others. Communication protocol Types of PLC programming languages There is diversity within programming languages because users have different training in different branches of engineering, for example, electrical and electronic engineers or technicians are used to using symbols in electrical diagrams, while systems engineers always use written languages, for which some prefer to program a more visual language and others prefer a written language. PLC programming languages can be classified into two classes, high and low-level languages each with different types. High-level languages In this category are the languages that are graphic, since they use a symbol interface to declare the control instructions, one of the disadvantages of these visual languages is that the programming is limited to the symbols that are provided. Ladder or ladder diagram This language was one of the pioneers since it was one of the first to be used since it closely resembles diagrams with relays. It is called ladder because it is very similar to the structure of a ladder since it contains two vertical rails, and several horizontal rails (in this case they would be the steps). Main features: The 2 vertical rails are power (in the case of VCD one is voltage and the other is ground and in VCA they are L1 and L2) Instructions are placed on the left side The exits are always placed on the right side. Multiple instructions or multiple outputs can be placed in parallel. The plc processor interprets the data from top to bottom and from left to right. Ladder Blocks diagram Logical symbol blocks are used in this type of programming. The outputs are not required to be incorporated into an output coil, because the output is assigned at the outputs of the logic blocks. These diagrams are mostly preferred by people accustomed to working with logic gate circuits since the symbology used is equivalent. Main features: The outputs of the blocks will not be connected to each other. The evaluation of a network is finished before starting the next Blocks diagram Block diagram Low-level languages In this type are the programming languages through text, using character strings to indicate the control instructions. Instruction list This type of language is the oldest and is the basis for all the programming languages that exist, this language is the precursor of the ladder diagram since it was used when computers did not yet have the graphical capacity. All languages are translated into instructions list. Main features: All languages can be translated to the instruction list, but not vice versa. Programming is more compact. This language is the most complete of all. Instruction list Structured text The structured text is made up of a series of instructions that can be carried out, as is the case with higher languages, on a conditional basis. This language is very similar to the C language and especially to PASCAL (“IF..THEN..ELSE”) or in sequential loops (WHILE..DO). Main features: Treats uppercase and lowercase letters interchangeably Supports complex arithmetic instructions.