Write a note on RS 485.

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written 6.2 years ago by

hetalgosavi • 1.6k

RS 485 is an Electronics Industries Association (EIA) standards interface which very common in data acquisition world.
RS 485 provides balanced transmission line which also can be shared in multidrop mode.
It allows high data rates communications over long distances in real world environments.
RS 485 was designed for greater distance and higher baud rates than RS – 232.
According to the standard, 100kbits/s is the maximum speed and distance up to 4000 ft (1200 meters) can be achieved.
Using RS -485, it is possible to construct a multipoint data communication network.
Protocol- half or full duplex, serial communication protocol
The Standard specifies that up to 32 drivers or transmitters along with 32 receivers can we used on a system.
This means that there can be 32 nodes capable to both transmit and receive.
This can be extended further by using “automatic repeaters” and high impedance drivers/receivers. This can be extended further by using “automatic” repeater and high impedance drivers/receivers. So, in this way it is possible to have hundreds of nodes on a network.
Logic level- electric signal is between +12V and -7V. Positive logic level is between 0V to 12 V (Logic 1) and Negative logic level is between -7V to 0 V (Logic 0).

RS 485 multtidrop network

Signal Interface

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