A-B 1756-TBCH/A 工控系统及装备

A-B 1756-TBCH/A 工控系统及装备

A-B 1756-TBCH/A 工控系统及装备

一些任务是间歇性的，但他们需要知道操作的后状态。这是一种典型的操作。要记住的是，什么构成一个模式?程序是怎样分配使得它满足两个要求?使用ALT指令能处理一种简单的这个/那个的情况。 这种编程形式在很多情况中可以见到。不过经常地，使用都略有不同。在某一场合中，一台机器可能被起动;在另一场合中，一个排气扇可能在循环与排气间转换。不同情况下，问题的初始表现并不能让人想起相同的解决方法。 对于本节的例子黑板擦来说，也是奴此。编程者的初始反应是它与起动一台机器或改变一个模式不一样。然而，如果忽略实际应用，只研究对象运行所要求的事件或序列，那么在这些不同的应用中能提取出相似之处。 这个目的不能独立地达到，因为实际问题确实访碍某些理想操作的发生。要记住的是，观察一个问题的方法不止一种，这个非常短小精悍的擦黑板程序就是其中一种方法。 PLC执行程序的过程分为三个阶段，即输入采样阶段、程序执行阶段、输出刷新阶段，PLC的扫描工作过程: （1）输入采样阶段。在这一阶段中，PLC以扫描方式读入所有输入端子上的输入信号，并将各输入状态存入对应的输入映像寄存器中。此时，输入映像寄存器被刷断。在程序执行阶段和输出刷新阶段中，输入映像存储器与外界隔离，其内容保持不变，直至下一个扫描周期的输入扫描阶段，才被重新读入的输入信号刷新。可见，PLC在执行程序和处理数据时，不直接使用现场当时的输入信号，而使用本次采样时输入到映像区中的数据。一般来说，输入信号的宽度要大于一个扫描周期，否则可能造成信号的丢失。

A-B 1756-TBCH/A 工控系统及装备

Some tasks are intermittent, but they need to know the post-state of the operation. This is a typical operation. Remember, what constitutes a pattern? How is the program allocated so that it meets two requirements? Using ALT command can handle a simple situation of this/that. This programming form can be seen in many cases. But often, the use is slightly different. On a certain occasion, a machine may be started; On another occasion, an exhaust fan may switch between circulation and exhaust. In different situations, the initial performance of the problem does not remind people of the same solution. For the example eraser in this section, it is also a slave. The programmer's initial reaction is that it is different from starting a machine or changing a mode. However, if we ignore the actual application and only study the events or sequences required by the object to run, we can extract similarities in these different applications. This goal cannot be achieved independently, because practical problems do hinder the occurrence of some ideal operations. Remember, there are more than one way to observe a problem, and this very short and pithy blackboard eraser program is one of them. The process of PLC program execution is divided into three stages, namely, input sampling stage, program execution stage and output refresh stage. The scanning process of PLC is: (1) input sampling stage. At this stage, the PLC reads in the input signals on all input terminals in a scanning way, and stores each input state in the corresponding input image register. At this point, the input image register is flushed. In the program execution stage and the output refresh stage, the input image memory is isolated from the outside world, and its contents remain unchanged until the input scanning stage of the next scanning cycle, when it is refreshed by the re-read input signal. It can be seen that when PLC executes programs and processes data, it does not directly use the input signals at the scene at that time, but uses the data input into the image area during this sampling. Generally speaking, the width of the input signal should be greater than one scanning period, otherwise the signal may be lost.

A-B 1756-TBCH/A 工控系统及装备