Figure 7-5. Configuration File Example 5
11/98 A-1 U0-1135
Westinghouse Proprietary Class 2C
Appendix A. Modbus Protocol
A-1. Section Overview
This appendix provides a brief overview of the Modbus protocol messages. It
should be useful for those with some Modbus protocol familiarity. A more detailed
description is available in PI-MBUS-300 “Modicon Modbus Protocol Reference
Guide” and on the world wide web at:
http://www.modicon.com/techpubs/toc7.html
Modbus is a registered trademark of Modicon, Inc.
A-2. Modbus Protocol Messages
Following are depictions of the Modbus functions supported by the LC/Modbus
Interface. The messages passed between the LC and the Modbus slave(s) can be
seen during operation by enabling analyzer mode as described in Section 4.
Figure A-1. Function 01 - Read Output (Coil) Status
Query
address function coil address no. of coils crc-16
Response
address function # bytes stat stat crc-16 ˜
˜ stat
stat 10101010 c+7 . . . c c = first coil
A-2. Modbus Protocol Messages
U0-1135 A-2 11/98
Westinghouse Proprietary Class 2C
Figure A-2. Function 02 - Read Input Status
Figure A-3. Function 03 - Read Holding Registers
Query
address function input address no. inputs crc-16
Response
address function # bytes stat stat crc-16 ˜
˜ stat

图7-5。配置文件示例5
1998年11月A-1 U0-1135
西屋专有2C级
附录A.Modbus协议
A-1。章节概述
本附录简要概述了Modbus协议信息。信息技术
对于那些熟悉Modbus协议的人来说应该很有用。更详细的
说明见PI-MBUS-300“Modicon Modbus协议参考”
“指南”和万维网上：
http://www.modicon.com/techpubs/toc7.html
Modbus是Modicon，Inc.的注册商标。
A-2。Modbus协议消息
以下是LC/Modbus支持的Modbus功能的描述
界面LC和Modbus从机之间传递的消息可以
如第4节所述，在运行期间通过启用分析仪模式查看。
图A-1。功能01-读取输出（线圈）状态
查询
地址功能线圈地址线圈编号crc-16
回答
地址函数#字节统计crc-16#
~stat
统计10101010 c+7。c=第线圈
A-2。Modbus协议消息
U0-1135 A-2 11/98
西屋专有2C级
图A-2。功能02-读取输入状态
图A-3。功能03-读取保持寄存器
查询
地址功能输入地址号输入crc-16
回答
地址函数#字节统计crc-16#
~stat