To correctly analyze and select suitable industrial network for application.we need to understand diffrent characteristics as listed below and most of these are objective of the network,efficiency,collision detection,topology(interconnection of cables), Distance (requirement of repeaters/bridges,switches etc),number of Devices etc….
- Data Formats for data exchange
In digital message number of bits are exchanged.the number of bits are divided in the field.each field carries information releted to the protocol.The actual message is stored in the data area
- Address Formats for data exchange
Addresses are used to identify both the sender and receiver.The address are stored in the header area of number of bit string.receiver are used that bitstring
- Address mapping
Sometimes protocols need to map addresses
- Detection of transmission errors
In networks which cannot give error free operation.crc is added end of frame or packets.The receiver rejects the packets on CRC differences and arranges for retransmission
In other terms we are also called hanshaking.acknowledgements of correct reception of packets are required for connection releated communication
- Loss of information
packets may be lost on the network.sender may expect an acknowledgement of correct reception from the receiver
- Direction of information flow
half duplex,full duplex
- Sequence control
Number of bit strings are divided in pieces and send on the network individually
TCP-Transmission control protocol
both are diffrent function and diffrent procedure that are often linked together.the term “TCP/IP”when information share over internet it is generally brocken up to smaller packets.and different parts of the message can be sent by different routes and then reassembled at the destination TCP is the means for the creating the packets,make correct order at the end and make sure no packets lost during transmission.Internet Protocol is the method used to route informtion to the proper address is known IP address.
HTTP(Hypertext Transfer Protocol) :
Web pages are constructed using HTML.is transmitted over the web using format known as HTTP(Hypertext Transfer Protocol) and it provide for the transmission in encrypted form form to provide security for sensitive data.
File Transfer Protocol(FTP) :
This is use for copying files over from one computer to another computer.its primary use is uploading files to a website.It can be used to be downloading from the web.
serial communication :
The concept of serial communication is simple.
The serial communication is slower than parallel communication.the important serial characteristics are baud rate,data bits,stop bits and parity.The Electronics Industry Association has give standard for RS485,RS422,RS232 .this are not protocol but it is media or electric interface
RS-232(ANSI//EIA-232 standard) is the serial connection found on a PCs.This is a single-ended data transmission.RS232 systems are recommanded for communication over short distances(up to 50 feet) and slower data rates.
RS-422(EIA RS-422-A Standard) it the serial connection used for large distance(up to 4000 feet)and at higher speeds(up to 10Mbps).this is suited for noisly environments.
RS-485(EIA-485 Standard):This is upgradation version of RS-422 and is specifically designed to communication with multiple device on a single data line.32 devices to communicate using the same data line.RS-485 is used physical layer.this most useful and common media of Profibus and Modbus.
This is serial communication protocol developed by modicon in 1979.is use with plc and is a master/slave protocol with half-duplex transmission most commonly available means of connecting industrial electronic devices.the main reasons are: Free protocol,ease of implementation,and comfortable with vendor
Industrial Ethernet is use local area network technology that transmit information between computer speeds of 10 and 100 Mbps and is a scalable technology with scalable bandwidth Ethernet signal are transmitted serially,one bit at a time.data is transmits the data in the form of packets