【正文】 r. The universal puter carries on into the information conversion, many only considered information itself, the information enters, so long as the manmachine contact surface were good may. But PLC then also must consider the information enters reliability, timeliness, as well as information question and so on use. Specially must consider how adapts in the industry environment, like is advantageous for the installment, question and so on. Programmable controllers realizations control main point enters the information conversion, the reliable physical realization, may say is the PLC realization control two basic main points. Enters the information conversion to depend on the movement to save in the PLC memory the procedure realization. The PLC procedure both has produces the factory the system program (not to be possible to change), and has the application which the user voluntarily develops (user) the procedure. The system program provides the movement platform, simultaneously, but also is the PLC procedure reliable movement and the signal and the information transformation carries on essential public processing. The user program according to controls the request design by the user. Any types control request, should have any type the user program. The reliable physical realization mainly depends on loses the person (INPUT) and the output (OUTPUT) the electric circuit. The PLC I/O electric circuit, all is specially designs. The input circuit must carry on the filter to the input signal, removes the high frequency interference. Moreover is isolates with 鞍山科技大學(xué)畢業(yè)設(shè)計(jì)（論文） 第 32 頁internal puter electric circuit on the electricity, depends on the light pair part establishment relation. Inside and outside the output circuit also is the electricity isolation, depends on the light pair part or the output relay establishment relation. The output circuit also must carry on the power to enlarge, to sufficiently drives the general industry control primary device, like solenoid valve, contact device and so on.The I/O electric circuit is very many, each entrance points either output all must have In or the Out electric circuit. PLC has multi I/O to use the spot, generally also has how many I/O point to use the electric circuit. But because they all are posed by the high integrate electric circuit, therefore, accounts for the volume not to be certainly big. The input circuit time is monitoring the input condition, and temporarily stores it to inputting in the temporary storage device. Each entrance point all has a corresponding the memory its information temporary storage device. The output circuit must output the latch the information transmission for the output spot. Output latch AND output also is 11 corresponding here input temporary storage devices and the output latch actually is PLC the processor I/O mouth register. They and puter memory exchange information through puter main line, and mainly by movement system program realization. Loses the person temporary storage device information to read PLC in the memory, called the input renovates. The PLC memory has the specially opening the depositing infer information mapping area. This area each corresponding position (bit) called it inputs the relay, or calls the soft contact. These positions bee 1, indicated the contact passes, sets at 0 to break for the contact. Because its condition is renovates by the input obtains, therefore, it reflects inputs the condition.Outputs the latch and in the PLC memory output mapping area also is the correspondence. An output latch also has a memory position (bit) if to correspond, this units place is called outputs the relay, or calls the output winding. Depends on the movement system program, outputs the relay the condition to map outputs the latch. This mapping also called the output renovates. The output renovates mainly also depends on the movement system program realization. Thus, the user must arrange the procedure only is, in the memory inputs the mapping area to the output mapping area transformation how 鞍山科技大學(xué)畢業(yè)設(shè)計(jì)（論文） 第 33 頁specially presses the input the succession to transform the output the succession. This is a data and the logical processing question. Because PLC has the formidable mand system, piles satisfies this request the procedure is pletely possible, moreover also is easier Programmable controllers realizations control way Calls the scanning way with this kind of unceasingly rerun procedure realization control. Is carries on the realtime control with the puter way. In addition, the puter uses in to control also has the severance way. Under the severance way, the control which must process first applies for the severance, after is responded the procedure which moves to stop moving, transfers but processes the severance work (movement related interrupt service). Treats processes the severance, also returns to the movement original procedure. Which control needs to process, which on applies for the severance. Which doesn39。t have to process, is not paid attention to. Obviously, the severance way and the scanning way are different. Under the severance way, the putation function obtains the full used, the urgent duty also can obtain prompt processing. But, how if simultaneously came the duty which how many all had to process to be supposed to manage? First rises also easy to do, is low? Possibly can appear the attendance not to arrive place. Therefore, the severance way not greatly suits to the job site daily use. But, PLC in uses in the scanning way primarily situation, also does not repel the severance way. Namely, the massive controls all uses the scanning way, individual urgent need processing, permissions severs this scanning movement the procedure, transfers but processes i