【正文】 除了 I/O 刷新及運(yùn)行用戶程序，還要做些公共處理工作。因?yàn)椋河辛溯斎胨⑿拢砂演斎腚娐繁O(jiān)控得到的輸入信息存入 PLC 的輸入映射區(qū)；經(jīng)運(yùn)行用戶程序，輸出映射區(qū)將得到變換后的信息；再經(jīng)輸出刷新，輸出鎖存器將反映輸出映射區(qū)的狀態(tài)，并通過輸出電 路產(chǎn)生相應(yīng)的輸出?？窟\(yùn)行系統(tǒng)程序，輸出繼電器的狀態(tài)映射到輸出鎖存器。它們與計(jì)算機(jī)內(nèi)存交換信息通過計(jì)算機(jī)總線，并主要由運(yùn)行系統(tǒng)程序?qū)崿F(xiàn)。如下圖所示： I/O 電路是很多的，每一輸入點(diǎn)或輸出點(diǎn)都要有一個(gè) I 或 O 電路。用戶程 序由用戶按控制要求設(shè)計(jì)。 I/O 分為開關(guān)量輸入 （ DI） ，開關(guān)量輸出 （ DO） ，模擬量輸入 （ AI） ，模擬量輸出 （ AO） 等模塊。模塊式 PLC 包括 CPU 模塊、 I/O 模塊、內(nèi)存、電源模塊、底板或機(jī)架，這些模塊可以按照一定規(guī)則組合配置。它源于繼電控制裝置，但它不像繼電裝置那樣，通過電路的物理過程實(shí)現(xiàn)控制，而主要靠運(yùn)行存儲(chǔ)于 PLC 內(nèi)存中的程序，進(jìn)行出入信息變換實(shí)現(xiàn)控制。 Maintenance simple, less maintenance。s third characteristic, will be further introduced Second, even if the PLC failure, the maintenance is very convenient. This is because the PLC had many failures presentation signals, such as PLC maintain support within the cell voltage insufficient data, the corresponding signals are low voltage directives. Moreover, the PLC itself is also a record of failure. Therefore, PLC, a failure, it is very easy diagnosis. At the same time, it is also diagnosed rear failure is simple. Pai it may module, the module can buy spare parts market, the replacement would be simple. As for software debugging good will not malfunctioning, so long as no adjustments based on the use of experience to perfect indulges. (5) To facilitate: PLC for certain equipment, if the equipment is no longer used, it could be used in the PLC to use other equipment, as long as this adaptation process is fulfilled. If the original equipment with new equipment is from the larger one, the number of modules therefore can be trusted. Reliable Work PLC control system used to achieve it is very reliable. This is because the PLC hardware and software in two aspects have taken many measures to ensure that it reliable. In fact, if PLC unreliable work cannot be used in industrial environments, will not make itself PLC In terms of hardware: PLC input and output circuit internal CPU is electricity segregation. photocoupling information is on the device or the transmission of electromagic devices. Moreover, the CPU board is resisting electromagic interference shielding measures. It will ensure that PLC operating procedures and magic interference from the outside world too normal. PLC use ponents for many of the noncontact, but also for the highly integrated, the number is not too large, but also provide a material foundation for its reliable. Structural design and manufacturing processes in mechanical, for PLC to secure work, has also taken many measures to ensure that PLC vibration resistant, high impact. Use of environmental temperature can be as high as over 50 degrees Celsius。 the individual can carry out emergency treatment. Actually the process of PLC is more plex than we mentioned here, the analysis of its basic tes, some theoretical issues. If the personnel on the above can enter a change, physical realization information processing, I/O call Cumming space, time scanning method supplemented by the interruption, as a way to study and understand it, and good understanding of PLC is how to achieve control and good grasp of the basic principles of PLC points. For more indepth, in the further course of study, will make a specific presentation. 5 Programmable Controller Basic Characteristics The operating principles are those from the discussion of PLC, PLC’s input and output are mutually separated in physics, which is linked to its existing storage operation on the procedures to achieve. It into a relevant, and not rely on physics, not a line。s functional procedures and data collection methods used by the scanning of the device or sent to the state data, and in the execution, at the same time, diagnostic power and the internal circuits PLC programming process and the work of the grammatical mistakes. During operation, from memory, the article retrieval user procedures is directively analyzed later by a corresponding directive mandates control signals to the mand control circuits. For example: CPU mainly by arithmetic unit, the controller, register and the links between them to achieve data, control and pose a challenge, CPU module also includes outlying chips, and the bus interface circuits. Procedures exist mainly for storage and data is an integral PLC modules. I/O Module PLC interfaces with the electrical circuit, and that is achieved through the importation of export segment (I/O) pleted. I/O module integration of the PLC I/O circuit, the input signal into Shortterm stored equipment reflects state export points also reflects export fliplatch state. Import module will be converted into digital signals into electrical signal PLC system, and the output module opposite. I/O into switching to import (DI), the export volume of switches (do), the volume of simulation (AI), analog output volume (AO) module Power Module PLC power provides power for the IC modules. At the same time, some of them also work for the importation of power circuit to provide 24V. Power input divided into types below: sharing power (220VAC or 110VAC), direct current power supply (monly used to 24VAC) 3 Programmable Controller Achieving Control Points Transformation of information I/O can be achieved by physical, which is could be considered to be two basic points. Information on their operations into and out of storage exists in the procedures of PLC. PLC procedures established manufacturers of the system procedures (irrevocable), and users develop their own applications (users) procedures. Operating system platforms provide procedures, and procedures for the PLC signal and reliable operation of the public with the information necessary conversion. Users control procedures designed by the users. What kind of control, due to what the user procedures. Reliable physical realization mainly relies on anyone else (input) and (output) circuit. PLC’s I/O circuits are specially