Table of Contents
Advertisement
What is Modbus?
1.6. What is Modbus?
This subsection discusses:
•
Modbus/RTU
•
Modbus/ASCII
on Page 17
•
Modbus/TCP
on Page 18
1.6.1. Modbus/RTU
Modbus/RTU is native Modbus in hexadecimal format. These are the base Modbus messages that contain
simple read and write requests. The format is as follows:
Where:
•
The terms Master or Client are used to identify the sender of the message.
•
The terms Slave or Server are used to identify the devices responding to the message.
Modbus/RTU is used primarily for:
•
Serial port connectivity
RS-485 is the most common serial mode, but RS-232 and RS-422 are also widely used. Commonly used by
both Master and Slave devices.
•
Ethernet TCP/IP socket connections
This is not the same as
remote devices. It is used by many applications and some OPC servers.
Note: This communication method typically is not supported by PLCs.
16 - Chapter 1. Introduction
Modbus/TCP
on Page 18, but does provide a very simple method of interfacing to
DeviceMaster EIP-MOD User Guide: 2000664 Rev. A
Advertisement
Table of Contents
Troubleshooting
