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一、前言在许多场合的分布式微机控制系统中,经常涉及各基本控制器 BCU(Basic Controlunit)和上位监控机间的数据通信。这种通信系统的网络结构如图1。为主从幅射式。它有如下特点:(1)任何一次数据通信都由主机发动,从机不主动发起通信行为。(2)一旦主从机建立了通信联系,要求能以全双工方式工作。即主从机能同时向对方发送和接收数据。(3)主机与各从机进行通信是分时进行的。即在某一时间间隔内主机只与某一个从机通信。各从机分时占用通信时间。(4)数据通信不能影响主从机执行主
I. Introduction In many occasions, the distributed microcomputer control system often involves data communication between the basic control unit (BCU) and the supervisory control unit. The network structure of this communication system is shown in FIG. 1. The main from the radiance. It has the following characteristics: (1) any one data communication is initiated by the host, from the machine does not initiate communication. (2) Once the master and slave establish a communication link, required to work in full duplex mode. Master and slave that can send and receive data to each other at the same time. (3) The host and the slave communication is time-sharing. That is, the host communicates with only one slave within a certain time interval. Each slave time-sharing communication time. (4) data communication can not affect the master and slave executive