LS Industrial Systems XGB Series - Modbus TCP;IP Protocol; General; Structure of Modbus TCP;IP Frame

Chapter 5 Protocols of Various Services
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5.3 Modbus TCP/IP Protocol
5.3.1 General
Modbus TCP/IP protocol function is to data Read/Write by using function codes. Modbus TCP/IP frame is composed of MAC, IP
Header, TCP Header, Modbus ADU for Enet communication.
(1) ADU : Application Data Unit
(2) MBAP : MODBUS Application Protocol
(3) PDU : Protocol Data Unit
5.3.2 Structure of Modbus TCP/IP frame
(1) Structure of Modbus TCP/IP frame through Enet
IP HeaderMAC TCP Header MODBUS TCP/IP ADU
MODBUS TCP/IP ADU
Ethernet Request / Response Frame
[Figure 5-3] Structure of Modbus TCP/IP frame through Enet
MABP Header
Transaction Identifier Protocol Identifier Length Unit Identifier
[Figure 5-4] Structure of Modbus TCP/IP ADU
MABP Header Function Code Data
MODBUS TCP/IP ADU
PDU
[Figure 5-5] Structure of Modbus ADU