Definition of the PLC

There are many definitions PLC. International Electrotechnical Commission (IEC) is the definition of the PLC: Programmable Logic Controller is a digital electronic computing plc analog input output io module operating system, designed for applications in industrial environments. It uses a programmable memory, used in its internal storage to perform logical, sequential control, timing, counting and arithmetic operations such as operating instructions, and through digital and analog inputs and outputs, control types machinery or production processes. Programmable logic controller and related equipment, all with industrial control systems should be easy to form a whole, to expand the principles of the design of its functions. The mid-1980s to the 1990s, is the fastest growing PLC period, the plc analog input output module annual growth rate has been maintained at 30 to 40 percent. During this period, PLC capability in handling analog and digital computing power, man-machine interface capabilities and network capabilities have been greatly improved, PLC gradually entering the field of process control, in some applications in the field of process control to replace the dominant DCS systems. PLC has the versatility, ease of use, wide adaptation, can be * high anti-jamming capability, programming and simple. PLC in the industrial automation and control especially in order to control the position, in the foreseeable future, can not be replaced.　

CPU configuration

CPU is the core of the PLC, acts as the nerve center of each PLC have at least one CPU, which functions according to the program given to the PLC system to receive and store user programmable logic controller programs and data collected by way of scanning the input device sent by the field state or data, and stored in the specified register, while the diagnostic power and the PLC internal circuit operating status and programming syntax errors. After entering the run, one by one to read the instructions from the user program memory, then the task was analyzed by Directive generate corresponding control signals to command associated control circuitry. CPU mainly by the operator, controller, register and data connections between them, control and status bus constituted, CPU unit also includes a peripheral chip bus interface and related circuitry. The main memory used to store programs and data, is an indispensable component PLC unit. In the user view, unnecessarily detailed analysis of the internal circuitry of the CPU, but each plc digital input output io module part is working mechanism should be enough to understand.CPU controller controls the work, which it reads the instruction, the instruction interpretation and execution of instructions. However, the pace of work is controlled by the oscillation signal. Operator used for digital or logic operations, working under the command of the controller. Register to participate in operations, and store intermediate result of the operation, it is also working under the command of the controller. CPU speed and memory capacity are important parameters for the PLC, which determines the operating speed of the PLC, IO, and the number of software capacity, etc., thus limiting the size of the control.

plc cpu common programming language

There in the plc cpu in a variety of programming languages, they are ladder language, Boolean mnemonic language, the language menu map, function block diagram language and structured description language statements. Ladder language and Boolean mnemonic language is the basic programming language, which is usually composed of a series of instructions, use these instructions to complete most simple control functions, for example, instead of relays, counters, timers complete plc cpu module sequence control and logic control etc., through the expanded or enhanced instruction set, they can also perform other basic operations. Function Charts language and sentence description language is an advanced programming language, it can be more efficient to perform the operation if necessary, for example, analog control, manipulation, newspaper printed statements and other plc digital input output io module basic programming language data can not be completed function. Function block diagram language in the form of a functional block diagram of the completion of the required control functions connected by way of a soft, it has not only been widely used in the programmable logic controller, while the programming and configuration of distributed control systems are also often be used, because it has to connect, easy to operate, easy to master, etc., for the majority of the engineering design and application staff favorite.