ModBUS 协议具有侦错能力强、数据传输量大、实时性好等特点，因而成为目前自控
领域使用非常广泛的通讯语言。本文通过一个应用实例介绍如何利用微机编程实现在线通讯ModBUS 消息环的工作过程，在可视化语言环境下完成地址域、功能代码域、数据域的分配及CRC 校验，从而实现计算机与远程控制单元数据传输。
关键词：ModBUS 协议、查询、回应、RTU 模式、CRC 校验。
Abstract: ModBUS protocol have powerful data transmittability , detectability and
realtime processing capability, so it had become a communication language that applicate widely in autocontrol field at present. This paper introduced a instance , how it realized a process about ModBUS structure of message loop and communication online, besides it created a frame which included address field ,option code field ,data field and CRC checking in visual programming environment, and send the
frame to Remote Termimal Unit.
Keyword: ModBUS protocol、query、reply、RTU mode、CRC check.
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