EP Series User Manual
16
3. Communication
3.1. Modbus/TCP introduction
Modbus is a communication protocol developed by MODICON in 1979 and is an
industrial field bus protocol standard. In 1996, Schneider introduced the MODBUS
protocol based on Ethernet TCP/IP-ModbusTCP. Modbus is an application layer
messaging protocol used for client/server communication between devices connected
on different types of buses or networks.
MODBUSTCP is a transmission protocol running on TCP/IP, (IANA-Internet
Assigned Numbers Authority) assigned port 502 for MODBUS/TCP, which is the only
port assigned in the instrumentation and automation industry at present.
It is usually used in the following media:
TCP over Ethernet;
Various asynchronous serial transmission media: RS-232, RS-422, RS-485.
Figure 3-1 Modbus application layer
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