3BSEO24388R3 PFXA401F ABB 控制单元多路传输控制单元
PFXA401SF 3BSEO24388R4工控PLC系统模块现货
控制单元，英文Control Unit(Cu)，是CPU部件之一，有时也安装与CPU外部。其基本功能是从内存取指令、分析指令和执行指令。控制单元是实现一种或多种控制规律的控制仪表或控制部件。如:多路传输控制单元、代理设置控制单元。
无论哪一个种类的控制单元，原理均为通过控制单元发出的控制信号对CPU各个部分加以控制。控制单元大体可以分为以下两类。微程序式，由微程序读取和发出控制信号。通过被称为微型定序器的简单数字通路（微型电脑）对微程序加以执行。
硬件型控制单元。由数字通路直接发出控制信号。由于集成电路的规模化及设计技术的进步，此种控制单元已成为可能
它根据用户预先编好的程序，依次从存储器中取出各条指令，放在指令寄存器IR中，通过指令译码(分析)确定应该进行什么操作，然后通过操作控制器OC，按确定的时序，向相应的部件发出微操作控制信号。操作控制器OC中主要包括节拍脉冲发生器、控制矩阵、时钟脉冲发生器、复位电路和启停电路等控制逻辑。通过硬件和软件侦听的方法，分析PLC内部固有的PPI通讯协议，然后上位机采用VB编程，遵循PPI通讯协议，读写PLC数据
实现人机操作任务。这种通讯方法，与一般的自
由通讯协议相比，省略了PLC的通讯程序编写，只需编写上位机的通讯程序资源
S7-226的编程口物理层为RS-485结构，SIEIMENS提供McroWin软件，采用的是PPI(Point to Point)协议，可以用来传输、调试PLC程序。在现场应用中，当需要PLC与上位机通讯时，较多的使用自定义协议与上位机通讯。在这种通讯方式中，需要编程者首先定义自己的自由通讯格式，在PLC中编写代码，利用中断方式控制通讯端口的数据收发。采用这种方式,PLC编程调试较为烦琐，占用PLC的软件中断和代码资源，而且当PLC的通讯口定义为自由通讯口时，PLC的编程软件无法对PLC进行监控，给PLC程序调试带来不便。SIEMENS S7-20PLC的编程通讯接口，内部固化的通讯协议为PP协议，如果上位机遵循PP协议来读写PLC，就可以省路编写PLC的通讯代码。如何获得PPl协议?可以在PLC的编程软件读写PLC数据时，利用第三个串口侦听PLC的通讯数据，或者利用软件方法，截取已经打开且正在通讯的端口的数据，然后归纳总结，解析出PPl协议的数据读写报文。这样，上位机遵循PPI协议，就可以便利的读写PLC内部的数据，实现上位机的人机操作功能。软件设计
3BSEO24388R3 PFXA401F ABB Control Unit Multiplex Transmission Control Unit
PFXA401SF 3BSEO24388R4 industrial control PLC system module in stock
Control Unit (Cu), also known as Control Unit, is one of the CPU components and is sometimes installed externally to the CPU. Its basic function is to fetch instructions from memory, analyze instructions, and execute instructions. A control unit is a control instrument or component that implements one or more control laws. For example: multiplex transmission control unit, proxy setting control unit.
Regardless of the type of control unit, the principle is to control various parts of the CPU through control signals sent by the control unit. Control units can generally be divided into the following two categories. Microprogram style, where control signals are read and issued by the microprogram. The microprogram is executed through a simple digital path (microcomputer) called a mini sequencer.
Hardware type control unit. Directly issuing control signals through digital channels. Due to the scaling of integrated circuits and advancements in design technology, this type of control unit has become possible
It sequentially retrieves each instruction from the memory based on the user’s pre programmed program and places it in the instruction register IR. Through instruction decoding (analysis), it determines what operation should be performed. Then, through the operation controller OC, it sends micro operation control signals to the corresponding components according to the determined timing. The operating controller OC mainly includes control logic such as beat pulse generator, control matrix, clock pulse generator, reset circuit, and start stop circuit. Analyze the inherent PPI communication protocol within the PLC through hardware and software listening methods, and then use VB programming on the upper computer to read and write PLC data following the PPI communication protocol
Implement human-machine operation tasks. This communication method is different from the general self
Compared to the communication protocol, the PLC communication program is omitted, and only the communication program resources of the upper computer need to be written
The physical layer of the programming port of S7-226 adopts an RS-485 structure, and SIEIMENS provides McroWin software using the PPI (Point to Point) protocol, which can be used to transmit and debug PLC programs. In on-site applications, when communication between PLC and upper computer is required, custom protocols are often used for communication with upper computer. In this communication method, the programmer needs to first define their own free communication format, write code in the PLC, and use interrupt methods to control the data transmission and reception of the communication port. Using this method, PLC programming and debugging is relatively cumbersome, occupying software interrupts and code resources of the PLC. Moreover, when the communication port of the PLC is defined as a free communication port, the programming software of the PLC cannot monitor the PLC, which brings inconvenience to PLC program debugging. The programming communication interface of SIEMENS S7-20 PLC has a fixed communication protocol of PP protocol. If the upper computer follows the PP protocol to read and write the PLC, it can save the time to write the PLC communication code. How to obtain the PPl protocol? When reading and writing PLC data in the programming software of the PLC, a third serial port can be used to listen for communication data from the PLC, or software methods can be used to intercept data from open and communicating ports, and then summarize and parse the data reading and writing messages of the PPl protocol. In this way, the upper computer follows the PPI protocol and can conveniently read and write internal data of the PLC, achieving human-machine operation functions of the upper computer. software design
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