Pilz PNOZ mmc1p ETH User Manual download pdf (Page 9)

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2-1

2.1 Modbus/TCP - Basics

2 Communication via Modbus/TCP

22000Communication via Modbus/TCPCommunication via Modbus/TCP2-2.1 Modbus/TCP - Basics2100 Modbus/TCP - Basics2-ModbusTCP_Modbus/TCP Allg-1

Modbus is an open fieldbus standard published by the User Group

MODBUS-IDA (see www.Modbus-IDA.org).

Modbus/TCP is a protocol based on Industrial Ethernet (TCP/IP over

Ethernet). It is a protocol with Client/Server communication. Data is

transferred via a request/response mechanism using function codes

(FC).

Modbus/TCP is connection-oriented, i.e. before usable data is trans-

ferred via Modbus/TCP, a connection must first be established between

two Modbus/TCP interfaces. The initiator of the connection is called the

Client. The communications partner with which the Client establishes

the connection is called the Server. Whether a connection on a device

assumes the role of Client or Server is defined when a connection is con-

figured. As a result, the Server/Client role only applies for the used con-

nection.

Application Layer

Protocol

Modbus/TCP

TCP

(RFC 793)

(RFC 791)

Industrial Ethernet

Physical Layer

Ethernet

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Pilz PNOZ mmc1p ETH User Manual Page 9