PAS 62030:2004 pdf download Digital data communications for measurement and control – Fieldbus for use in industrial control systems – Section 1: MODBUS® Application Protocol Specification V1.1a – Section 2: Real-Time Publish-Subscribe (RTPS) Wire Protocol Specification Version 1.0
1 MODBUS
1.1 Introduction
1.1.1Scope of this section
MODBUS is an application layer messaging protocol, positioned at level 7 of the OSl modelthat provides client/server communication between devices connected on different types of
buses or networks.
The industry’s serial de facto standard since 1979, MODBUS continues to enable millions ofautomation devices to communicate. Today, support for the simple and elegant structure ofMODBUS continues to grow. The lnternet community can access MODBUS at a reservedsystem port 502 on the TCP/IP stack.
MODBUS is a request/reply protocol and offers services specified by function codes.MODBUS function codes are elements of MODBUS request/reply PDUs. The objective of thisPAS is to describe the function codes used within the framework of MODBUS transactions.
MODBUS is an application layer messaging protocol for client/server communication betweendevices connected on different types of buses or networks.
t is currently implemented using:
。TCP/IP over Ethernet. See Annex A of Section 1: MODBUS MESSAGING ON TCP/IPIMPLEMENTATION GUIDE
Asynchronous serial transmission over a variety of media (wire : EA/TIA-232-E, EIA-422-A.EIA/TIA-485-A; fiber,radio,etc.)
。MODBUS PLUS,a high speed token passing network.NOTE The”Specification” is Clause 1 of this PAS
NOTE MODBUS Plus is not in this PAS.
1.1.2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 61131 (all parts): Programmable controllers
EIA * /TIA ** -232-E: Interface between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary data Interchange
EIA-422-A: Electrical Characteristics-Balanced Voltage Digital Interface Circuit
EIA/TIA-485-A: Electrical Characteristics of Generators and Receivers for Use in balanced Digital Multipoint Systems
RFC 791, Interne Protocol, Sep81 DARPA
1.2 Abbreviations
ADU Application Data Unit
HDLC High level Data Link Control
HMI Human Machine Interface
IETF Internet Engineering Task Force
I/O Input/Output
IP Internet Protocol
MAC Medium Access Control
MB MODBUS Protocol
MBAP MODBUS Application Protocol
PDU Protocol Data Unit
PLC Programmable Logic Controller
TCP Transport Control Protocol
1.3 Context
The MODBUS protocol allows an easy communication within all types of network architectures.
Every type of devices (PLC, HMI, Control Panel, Driver, Motion control, I/O Device…) can use MODBUS protocol to initiate a remote operation. The same communication can be done as well on serial line as on an Ethernet TCP/IP networks. Gateways allow a communication between several types of buses or network using the MODBUS protocol.

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