【正文】 error. Currently the HMI factory is also more and more, the function is also more and more strong, the price is also more and more low, and the noodles of the usage are wide more and more. The HMI foreground can say that think 176。 But lead even is a fatal error greatly is what we can39。 The I/ O add inner part is tired the input and output system of the machine and exterior link, and deposit the related data into the procedure saving machine or data saving machine。 Another kind of highspeed work, USES the token passing mode munication, munication rate of 1 m to 10 MBPS, transmission distance is 500 ~ 1000 m, 1024 online nodes. These two types of works are linked together, can be patible with different types of programmable controller and puter, forming control range a lot of local work. 5. Easy to install, easy to maintain. PLC installation is simple and powerful functions, its relatively small size allows them to install the relay control box usually required for half of the space. In the large PLC system installation, remote I/o in the optimal location. Remote I/O station through double axis of coaxial cable, or even to the CPU, which greatly reduces the material and labor, remote subsystem method means from different parts of the system can be installed in field. Because almost all of the ponents are modular, only need to change when maintaining module level plugin ponents, fault detection circuit diagnosis indicator will be embedded in each part, can indicate the device is working correctly, the resistance in programming is visible input/output devices ON or OFF, still can write programming instructions to report failures. In addition, PLC automation technology, puter technology and munication technology together, and you can also plete the following functions: logic control, timing control, counting control, stepper control, A/D and D/A conversion, data processing, munication work and monitoring on the control system. In general, the application of PLC have boom in the world, the PLC development direction mainly toward miniaturization, deflationary force, standardization, standardization, intelligence, high speed, large capacity, ne twork development, this will make the PLC function is stronger, higher reliability, more convenient use, wide application and more The PLC biggest characteristics lie in: The electrical engineering teacher already no longer electric hardware up too many calculations of cost, as long as order the importation that the button switch or the importation of the sensors order to link the PLC up can solve problem, pass to output to order the conjunction contact machine or control the start equipments of the big power after the electric appliances, but the exportation equipments direct conjunction of the small power can. PLC internal containment have the CPU of the CPU, and take to have an I/ O for expand of exterior to connect a people39。 外文文獻 PLC technique discussion and future development Programmable Controller (Programmable Logic Controller, customarily referred to as PLC) is a microprocessor as the core of the general industrial automation devices. Is in the late 1960 s in the relay control system developed on the basis of, it will traditional relay control technology bined with puter technology and munication technology, has a simple structure, superior performance, high reliability, flexible, general and convenient use, easy to programming. In particular, the characteristics of the PLC is shown as the following Aspects: (1) the high reliability of hardware. PLC is specialized in industrial environment under the conditions of application and design. Can be placed in a well designed PLC has a very high voltage noise, electromagic interference and mechanical vibration, extreme temperature, and humidity environment. Is in the aspect of hardware design, first of all with high quality ponents, and adopt reasonable system structure, strengthening, simplify installation, makes it easy to anti vibration shock, to the printed circuit board design, machining and welding process are taken very strict measures, and on the circuit, the structure and process had taken some unique ways. Because the PLC itself has very high reliability, so in the event of a failure parts mostly focused on the input/output parts and such as sensors, limit switches, photoelectric switch, electromagic valve, motor, etc. programming and easy to use. Automatic control by microputer, monly used assembly language programming, difficult to grasp, requires the user has a certain level of knowledge of puter hardware and software. PLC used for process control, problem oriented programming method, pared with the currently used assembly language microputer control, while inside the PLC increases the interpretation procedure, to increase the program39。例如，在一些局域網(wǎng)系統(tǒng)中，這些鏈接可以在相對高的傳輸速度和范圍之前，需要一個中繼距離長。光纖電纜是幾乎不受惡劣的環(huán)境條件和電氣噪聲。運行在較短（少于 50 英尺），數(shù)據(jù)傳輸可以達到 10 Mbps 的。其主要方面包括各信號的信號地面兩條電線是在相 反的邏輯電平始終。 當傳輸距離更長，還需要的 RS422 是一個更好的選擇。雖然 RS232C裝置往往可以達到比這更大的布線距離的 “不平衡 ”在更大的敏感性結果的界面設計，周圍的電噪音和降低數(shù)據(jù)完整性。 他們的實際表現(xiàn)是傳動裝置制造商之間的功能和顯著變化。最大傳輸速度為 Kbps。 網(wǎng)絡傳輸接口 PLC 的通信絕大部分都是通過 RS232C 及雙絞線電纜。 調制：調制是指網(wǎng)絡郵件的方式傳輸編碼的電纜進行測試。 專有的協(xié)議是唯一的消息的安排，并由他們與該供應商的產品只能使用特定的供應商開發(fā)的編碼。 議定書：網(wǎng)絡協(xié)議的方式界定和安排的信息在局域網(wǎng)上傳輸編碼。令牌傳遞從節(jié)點到節(jié)點，使每個有機會傳送不受干擾。如果兩個節(jié)點同時傳輸，碰撞檢測和兩個節(jié)點轉發(fā)，直到他們的消息通過正常。有兩種常見的訪問方法。 訪問，協(xié)議和調制功能的局域網(wǎng) 通過使用標準的接口和協(xié)議，允許局域網(wǎng)的設備組合（可編程控制器，個人電腦，電腦主機，操作界面終端 等），從許多不同的供應商進行通信與網(wǎng)絡上的其他人。這個模塊基本上是一個小型計算機插入 PLC 的巴士。它的 PLC 程序員有責任提供必要的軟件接口。雖然很多智能設備可以通過傳統(tǒng)的 RS232C 通信端口和串行ASCII 碼的 PLC 直接，一些沒有能力的軟件接口與 個人的 PLC 型號。這樣，你可以創(chuàng)建，修改，調試，并通過計算機終端顯示器 PLC 程序。強大的編程和文檔軟件方案可供開發(fā)。這個周期發(fā)生每秒數(shù)百次。這臺計算機的網(wǎng)絡地址單獨的 PLC 和每一個具體的信息要求。這種電腦組合，最大限度的控制功能的 PLC 控制和數(shù)據(jù)采集，以及計算機，數(shù)據(jù)處理，文件和操作界面。 主機電腦聯(lián)系 也可連接的 PLC 與計算機或其他智能設備。但是，它可能指定作 為掌握 PLC的一組作為一個控制器類型使用。因為所有通信發(fā)生對用戶透明，通訊編程是減少到簡單的讀取和寫入報表。 同儕對同儕網(wǎng)絡，每個網(wǎng)絡中的 PLC 是為自己負責控制現(xiàn)場，只需要為它自