Editing Process control network

{{More citations needed|date=May 2015}}

A '''Process Control Network''' (PCN) is a communications [[telecommunications network|network]] layer that is a part of the [[Industrial Automation networks in Process Industries]]. This network is used to transmit instructions and data between control and measurement units and Supervisory Control and Data Acquisition ([[SCADA]]) equipment.

==Industry requirements==
These networks have, over the years, used many of the technologies and topologies utilised in other network applications. However, Process Control Networks (PCNs) have several special requirements that must be met in order for the solution to be acceptable to the industry. These requirements are, in no particular order: Robustness, Determinacy, Compatibility. Robustness includes requirements such as connection redundancy, reduced sensitivity to [[Radio Frequency Interference|Electromagnetic Interference]] (EMI), and good error checking and correction. Determinacy involves assuring that each device is guaranteed access to the network, and in many cases mechanisms to allow priority information (such as alarms) through the system. Compatibility allows SCADA and [[Distributed Control System]]s (DCS) from various manufacturers to communicate with control and measurement equipment from others.

==Development of standards== 
Many early PCNs were serial based, using low level standards such as [[Electronic Industries Alliance|EIA]] [[RS-422]] and EIA [[RS-485]] with proprietary [[Communications protocol|protocols]] on top. One of the [[de facto]] [[standardization|standard]]s (which is now becoming an [[open standard]]) is [[Modbus]], originally from Modicon. Many PCNs used [[token passing]] based protocols because they are essentially deterministic. Both [[Allen Bradley]] and [[Eurotherm]] utilised such mechanisms. Many of the measurement and control unit manufacturers signed up to the Fieldbus consortium but rather than one standard emerging each manufacturer promoted their own 'standard' leading to a myriad, and confusing, range of physical and [[logical system]]s. Modern process control networks rely on Ethernet, TCP/IP, and Microsoft Windows technology.<ref>{{cite web|url=http://energy.gov/sites/prod/files/Good%20Practices%20Guide%20for%20Firewall%20Deployment.pdf|title=Good practice guide on firewall deployment for SCADA|date=15 February 2005|website=energy.gov|access-date=30 July 2023}}</ref>

==References==
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{{DEFAULTSORT:Process Control Network}}
[[Category:Networks]]