Introduction Of RS-422
There are various devices in digital headend which have the serial port for the communication with another device. The most widely used port is RS-232 Serial Port for serial communication. Which can be 3 PIN, 9 PIN or even 25 PIN. While on the other hand there is one more serial port for communication known as RS-422.
So in this article we will cover What Is RS-422 Serial Communication Port and its working with diagram.
What Is RS-422 ?
RS-422 is the advanced communication technique of RS-232 serial communication. It is advanced version because it overcome the limitations of RS-232 communication.
The RS-232 cable is having maximum length of 50 feet and 19.2 K Baud rate. So the distance and data rate is very low to use. If we increase the length of RS-232 port cable then it gives high data loss with low data transfer rate. To overcome this problem new Serial Communication Protocol RS-422 was released.
RS-422 serial communication protocol have faster speed and good cable length than RS-232 serial communication protocol. RS422 is having 9 PIN connector known as DB9.
We have already covered RS-232 Serial Communication Port briefly in our other article Click Here
Working Of RS-422 ?
As shown above in the figure there is one Server connected left side with a STB right side with RS-422 serial communication port. total 5 number of connectors are used in which ground is connected directly for both connectors.
At the Server Side RS 422 Serial Communication Port,
TD(B)+ To RD(B)+ And T(D)A- To R(D)A- = Two conductors for sending the data from the Server to STB.
TD(B)+ To RD(B)+ And T(D)A- To R(D)A- = Two conductors for receiving the data from the STB to Server.
So there are total 5 cables used in RS-422 serial communication protocol. In which 2 used for data transmission and two used for data reeving while one is used for Ground.
The RS-422 Serial Communication Protocol is faster than RS 232 because it uses differential transmission technique. Which is also known as Balanced Transmission Technique. In this transmission technique there is a potential difference between two conductors.
Thus two conductors are used for transmission and reception which means no interference problem because interference occurs on both conductors and data is collected from these conductors due to potential difference of conductors.
So the cable length for the RS 422 Serial Port can be 50 feet at the speed of 10 Mbps data rate. Also it can be 4000 feet for data rate of 100 Kbps.
RS 422 consume low power than RS-232. The range of voltage on conductor can be -6 Volt to +6 Volt. The range of -2 Volt to +2 Volt is good nose margin for the system.
RS 422 port uses the same connector used for RS-232 port. There is also a converter available to convert the RS 422 into RS-232.
RS 422 port uses Full Duplex transfer type. .Maximum 10 number of receivers can be connected from one transmitter.
Conclusion Of RS-422
RS-422 is a faster and reliable serial communication protocol to establish a connection between two devices by using DB9 connector. Faster delivery of data with good cable length are two advantages of this RS 422 serial communication protocol. It is used in Apple Macintosh Computers.
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