Monday, September 26, 2011

A Translation Method of Ladder Diagram on PLC





Programmable logic controller (PLC) was initially built up to substitute circuit of electro magnetic relay. It is generally utilized for applying systems according to timing, counting, logic, arithmetic, and sequencing. PLCs are the strength of character of most projects of automation the instrumentation sector and process control. Production lines automation and processes of manufacturing will guide to the growth of the less of manpower factory where there is no longer any major requirement for workers or operators production. Such automation levels will not be realizable with no control systems development, mostly PLCs.

As a progress of automation systems, works that the PLC performs turn into more complicated. It has maintained more than a hundred kinds of instructions to care for them proficiently of the instructions the special instructions proportion for example PID and operations of coating point has been enlarged with the addition of its flexible range. These instructions require much time to implement. The time of execution the program of PLC, this work is supported in part by the POSCON, Ltd. Korea is vital as a determine of its presentation. Therefore, enlarge of instructions places a load to presentation of the PLC. To advance speed of the architectures of PLC of a new processor have been recommended. They built up particular processors for PLC to elevate its performance, with parallel methods of processing, or specific application of the design methods of IC ASIC. For instance, researches on decreased instruction set RISC computer place characteristic instructions of the PLC into a specific processor of PLC. This technique looks efficient to enlarge the speed of execution. But it is hard to attach new instructions to the processor and to build up it within a short time.

The PLC according to a universal purpose processor has fewer presentation than one based on a particular reason processor. But the universal purpose processor has some realistic benefits. It has the performance curve price that raises at a very quick rate. It also can be produced at lower cost in a faster time throughout the enhancement correlated to the software. The PLC languages translators occupy a major software part. The translator should translate the LD to other code secure to the language of machine. But it is not simple to convert the LD graphical into the processor native code because of a semantic space between them. Existing techniques of translation have not believed it fatally. They translate a program of LD to codes of intermediate that contains matching of code with each PLC node. They get middle codes from the memory and after that call a corresponding routine of program block on their operation. They generally need a long time even on high presentation processors of RISC since they require many divisions. Accordingly, a technique is required to overcome low efficiency and slow speed of this conversion techniques.



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