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  • Subject area(s): Engineering
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  • Published on: 7th September 2019
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  • Number of pages: 2

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The computer at the top is masters and plc are the salves.

The communication between them is master to slave or slave to master.

Connection between the plc is peer to peer.

There are various proto calls and standards laying down the way they communicate

Networking standard used in plc are

• Master to slave

• Peer to peer

• ISO

• IEEE

• MAP

 Peer-to-peer networks

Peer-to-peer networks as shown in enhance reliability by decentralizing the control functions without sacrificing coordinated control

 PLC are connected to one another in a daisy chain fashion and a common memory table is duplicated in the memory of each.

 In this way, when any PLC writes data to this memory area the information is automatically transferred to all other PLCs in the network. It was used to operation of information

 With peer-to-peer networks each PLC in the network is responsible for its own control site and only needs to be programmed for its own area of responsibility.

The network significantly reduce  reduces programming and debugging complexity because all communications occur transparently to the user communications programming is reduced to simple read and write statements.

In a peer-to-peer system there is no master PLC. It’s possible to designate one of the PLCs as a master for use as a type of group controller.

 PLC can be used to accept input information from an operator input terminal for example sending all the necessary parameters to other PLCs and coordinating the sequencing of various events.

Master to slave method

• In computer networking, master to slave is a model for a communication protocol in which one device or process controls one or more other devices or processes

• Once the master to slave relationship is established the direction of control is always from the master to the slave

The County of Los Angeles saying the term master to slave may be offensive to some of its residents has asked equipment manufacturers not to use the term. Some manufacturers prefer the term primary to secondary.

ISO= INTERNATIONAL STANDERED ORGANISATION

• ISO International Standards ensure that products and services are safe reliable and of good quality.

• They are tools reduce by minimizing waste and errors and increasing productivity.

• They help companies to access new markets level the playing field for developing countries and facilitate free and fair global trade.

IEEE= INTITUTE OF ELECTRICAL AND ELECTRONIC ENGINEERS

• IEEE stands for the Institute of Electrical and Electronics Engineers

• IEEE membership has long been composed of engineers and scientists.

• Allied professionals who are members include computer scientists and software developers information technology professionals physicist and medical doctors in addition to IEEE electrical and electronics engineering core.

• The intuition no longer goes by the full name except on legal business documents and is referred to simply as IEEE.

MAP=MANUFACTURING AUTOMATION PROTOCAL

• The Manufacturing Automation Protocol was a computer network standard released in 1982 for interconnection of devices from multiple manufacturers.

• It was developed by General to combat the proliferation of incompatible communications standards used by suppliers of automation products such as programmable controllers.

• The standard was revised several times between the first issue in 1982 and MAP in 1987 with significant technical changes that made interoperation between different revisions of the standard difficult.

• Although promoted and used by manufacturers such as Boeing and others it lost market share to the contemporary Ethernet standard and was not adopted. Difficulties included changing protocol specifications the expense of MAP interface links and the speed penalty of a token passing network.

• The network protocol used by MAP became standardized as IEEE standard but this committee disbanded in 2004 due to lack of industry attention.

• This is token passing local area network configuration adopted by general motor for factory automation.

Networks definitions

LAN= local area network

ETHERNET

It is very common method used for networking computers in LAN using copper cabling. ETHERNET can handle 10,000,000 per sec and can be used almost any kind of computers.

INTERANET

It is general name for networks linking computers with in a private organisation such as college business and government departments

 They use standard network technologies like ETHERNET and web server. User connected to the INTERANET often access to the internet but a fire wall prevents external uses accessing it. Sometimes it will gives access to ETHERNET to provide control access to some outsider example government work access

EXTRANET

It is the private network that allows limited access to the specified user. It uses internet for links EXAMPLE bank with internet access for costumers protected by protocol

Network options

• PLC networks provide you with a variety of networking options to meet specific control and communications requirements.

• Typical options include remote peer-to-peer and host computer communications as well as LANs.

• These networks can provide cost effective communications between as few as two or as many as several hundred PLCs computers and other intelligent devices.

• The various communications protocols command sequences error checking schemes and communications media used by each manufacturer.

• However, it is possible to make different PLCs  to one another what's required is an ASCII interface for the connections along with considerable work with software

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