Modbus Rtu Cable Specification

This document comes in complement to the document called modbus application protocol specification.

Modbus rtu cable specification.

Modbus is a data communications protocol originally published by modicon now schneider electric in 1979 for use with its programmable logic controllers plcs. However the cable recommended for long lengths can be expensive so if there is an existing ethernet infrastructure in place it may be more affordable to convert from bacnet ms tp or modbus rtu over rs 485 to bacnet tcp ip or modbus tcp ip over ethernet. Please review the following license agreement before down loading any modbus protocol or related documents from this web site. Modbus is popular in industrial environments because it is openly published and royalty free.

If you agree to the terms herein then you must click the i accept button below before you are permitted to use this software protocol and related documents. Modbus has been a standard for interfacing remote i o and plcs into the process dlc system for over 20 years allowing most legacy control systems to interface easily with modbus. The message structure of the modbus rtu function codes is employed and standard ieee 32 bit floating point and integer formats are used. The cable shield must be earthed only in one point.

Networks system sds honeywell access4000system 9248 rg 6pvc foundationfieldbus se eprotocollistingsonpage4. Of slaves also depend on the data logger specification. Under ideal conditions cable lengths of 4000 ft. Modbus specifications and implementation guides.

General overview of modbus documents. In chapter 5 different implementation classes are defined for modbus serial line. The modbus rtu specification is respected in the physical and data link layers. 1200 m or more are possible.

Go back to modbus rs485 cabling rules 8. Normally this connection is made at one end of the main cable. Typesp50is a iec ipc620systemi o 9271 twinax 25awg 124ohm. Specification of a class is the sum of requirements that a device must respect in order to belong to that class.

In order to avoid signal reflections a 120 ohm termination resistance must be fitted on each end of. Data register mapping is unique to these instruments. Modbus cable interface quickly and easily with most existing plant control architectures by using belden cabling for modbus.