【正文】 usion The controller developed for this work (Fig. 11) shows that it is possible to create a very useful programmable controller based on microcontroller. External memories or external timers were not used in case to explore the resources that the microcontroller offers inside. Outside the microcontroller, there are only ponents to implement the outputs, inputs, analog input, display for the interface and the serial munication. Using only the internal memory, it is possible to control a pneumatic system that has a sequence with 48 steps if all the resources for all steps are used, but it is possible to reach sixty steps in the case of a simpler system. The programming of the controller does not use PLC languages, but a configuration that is simple and intuitive. With electropneumatic system, the programming follows the same technique that was used before to design the system, but here the designer work s directly with the states or steps of the system. With a very simple machine language the designer can define all the configuration of the step using four or five bytes. It depends only on his experience to use all the resources of the controller. The controller task is not to work in the same way as a mercial PLC but the purpose of it is to be an example of a versatile controller that is designed for a specific area. Because of that, it is not possible to say which one works better。它不需要為了獲取微控制器里的資源而安裝外部記憶器或外部的定時(shí)器。這些照片是控制線路的電圖表 ,包括感應(yīng)器，控制鍵和電的活瓣卷。利用回旋的 電流工作的主動(dòng)器 D連同返回來(lái)的 C一起工作。有兩個(gè)輸入端共同工作可以快速的運(yùn)行這些功能。 這種 控制器以微集成電路微控制器 PIC16F877 為基礎(chǔ) ,它擁有全部此次項(xiàng)目所需要的資源。 上述方法可以使發(fā)動(dòng)機(jī)的每一個(gè)運(yùn)動(dòng)都被很好地用步驟來(lái)定義。 針對(duì)這種情況可行的一種辦法是創(chuàng)建一個(gè)可提供特定尺寸和功能的控制器。 PLC 的感應(yīng)器和開(kāi)關(guān)是輸入端，而發(fā)動(dòng)機(jī)的直接控制閥是輸出端，其中有一個(gè)內(nèi)部程序操控所有運(yùn)行必需的邏輯，模擬其他的裝置如計(jì)算器、定時(shí)器等 ，對(duì)整個(gè)系統(tǒng)的運(yùn)行狀態(tài)進(jìn)行控制。這是就需要另一種方法可以節(jié)省時(shí)間，產(chǎn)生清晰線路，能夠防止偶然的信號(hào)交疊和線路堵塞。 在編程之后，部件序列被內(nèi)部微控制器的記憶所儲(chǔ)藏，因此，他們是可讀的而且可以運(yùn)行。 交互作用 在實(shí)際運(yùn)行操作中，控制器需要有一些輔助設(shè)備幫助它和使用者進(jìn)行互動(dòng)，可以提供可靠的操作監(jiān)控，同時(shí)對(duì)氣流系統(tǒng)進(jìn)行邏輯控制。 5 電氣系統(tǒng)例子 這種系統(tǒng)不只是適應(yīng)于特定的機(jī)器。 利用他們我們可 以用必需的邏輯語(yǔ)言設(shè)計(jì)整個(gè)的控制線 路。 那就是說(shuō)，使用傳統(tǒng)的 PLC，使用者清楚各個(gè)操作之間的關(guān)系。 each string has the configuration of one step of the process. There are two bytes for the inputs, one byte for the outputs and two more for the other configurations and auxiliary functions of the step. After programming, this sequence of strings is saved inside of a nonvolatile memory of the microcontroller, so they can be read and executed. The controller task is not to work in the same way as a conventional PLC, but the purpose of it is to be an example of a versatile controller that is design for an specific area. A conventional PLC process the control of the system using a cycle where it makes an image of the inputs, execute all the conditions defined by the configuration programmed inside, and then update the state of the outputs. This controller works in a different way, where it read the configuration of the step, wait the condition of inputs to be satisfied, then update the state or the outputs and after that jump to the next step and start the process again. It can generate some limitations, as the fact that this controller cannot execute, inside the program, movements that must be repeated for some time, but this problem can be solved with some external logic ponents. Another limitation is that the controller cannot be applied on systems that have no sequence. These limitations are a characteristic of the system that must be analyzed for each application. 4. Characteristics of the controller The controller is based on the MICROCHIP microcontroller PIC16F877 [6,7] with 40 pins, and it has all the resources needed for this project .It has enough pins for all the ponents, serial munication implemented in circuit, EEPROM memory to save all the configuration of the system and the sequence of steps. For the execution of the main program, it offers plete resources as timers and interruptions. The list of resources of the controller was created to explore all the capacity of the microcontroller to make it as plete as possible. During the step, the program chooses how to use the resources reading the configuration string of the step. This string has two bytes for digital inputs, one used as a mask and the other one used as a value expected. One byte is used to configure the outputs value. One bytes more is used for the internal timer , the analog input or timeout. The EEPROM memory inside is 256 bytes length that is enough to save th