Editing Modbus (section)

{{Short description|Serial communications protocol}}
{{Distinguish|Meter-Bus{{!}}M-Bus}}

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* Modicon (1979–1997)
* [[Schneider Electric]] (1997–2004)
* Modbus Organization, Inc. (since 2004)
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[[File:Logo of Modbus-IDA.svg|thumb|Logo of Modbus-IDA, the older name of the industry consortium ]]
'''Modbus''' or MODBUS is a client/server data [[communications protocol]] in the [[application layer]].{{Sfn|MODBUS Application Protocol|2012|p=2}} It was originally designed for use with [[programmable logic controller]]s (PLCs),{{Sfn|MODICON, Inc.|1996|p=|ps=, "Preface"}} but has become a ''[[de facto]]'' [[standardization|standard]] communication protocol for communication between industrial [[Electronics|electronic]] devices in a wide range of buses and networks.<ref name="Drury2009">{{cite book |first=Bill |last=Drury |title=Control Techniques Drives and Controls Handbook |edition=2nd |date=2009 |publisher=[[Institution of Engineering and Technology]] |url=https://app.knovel.com/kn/resources/kpCTDCHE08/toc |format=PDF |pages=508– |url-access=subscription}}</ref>{{Sfn|MODBUS Application Protocol|2012|p=2}}

Modbus is popular in industrial environments because it is openly published and [[royalty-free]]. It was developed for industrial applications, is relatively easy to deploy and maintain compared to other standards, and places few restrictions on the format of the data to be transmitted.

The Modbus protocol uses [[serial port|serial communication lines]], [[Ethernet]], or the [[Internet protocol suite]] as a transport layer.{{Sfn|MODBUS Application Protocol|2012|p=2}} Modbus supports communication to and from multiple devices connected to the same cable or Ethernet network. For example, there can be a device that measures temperature and another device to measure humidity connected to the same cable, both communicating measurements to the same [[computer]], via Modbus.

Modbus is often used to connect a plant/system supervisory computer with a [[remote terminal unit]] (RTU) in supervisory control and data acquisition ([[SCADA]]) systems. Many of the data types are named from industrial control of factory devices, such as [[ladder logic]] because of its use in driving relays: a single-bit physical output is called a ''coil'', and a single-bit physical input is called a ''discrete input'' or a ''contact''.

It was originally published by Modicon in 1979. The company was acquired by [[Schneider Electric]] in 1997. In 2004, they transferred the rights to the Modbus Organization<ref>{{cite web |url=https://modbus.org/faq.php |title=Modbus FAQ |website=Modbus |publisher=Modbus Organization, Inc. |access-date=1 November 2012}}</ref> which is a [[trade association]] of users and suppliers of Modbus-compliant devices that advocates for the continued use of the technology.<ref>{{cite web |url=https://modbus.org/about_us.php |title=About Modbus Organization |website=Modbus |publisher=Modbus Organization, Inc. |access-date=8 November 2012}}</ref>