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RS-232 and RS-485

Introduction

RS-232 and RS-485 both belong to the serial interface family. A serial interface is a communication interface in which data is transmitted bit by bit. A high logical voltage is represented as “1” and a low logical voltage is represented as “0.”

Among all the serial interfaces in the market, RS-232 and RS-485 are the oldest ones and are still widely used.

RS-232

RS-232 stands for Recommended Standards 232. It was created in 1960 by the Electronic Industries Association (EIA) and is widely used in connecting computers and their peripheral devices. It provides a data rate of 1.42kbps and can send data up to 50 feet.

  1.  RS-232 working: RS-232 is used in connecting and transferring data between Data Transmission Equipment (DTE) and Data Communication Equipment (DCE). DTEs basically act as transmitters, while DCEs act as receivers. The following pins are used:
TXDTRANSMITTER
RXDRECEIVER
RTSREQUEST TO SEND
CTSCLEAR TO SEND
GNDGROUND

From DTE, RTS generates requests to send data to DCE. From DCE, CTS clears the path to receive the data and the data is sent. Similarly, RTS generates requests and is cleared by CTS to transfer data from DCE to DTE.

  1. Electrical specifications of RS-232: The following are the electrical specifications of RS-232:
    1. Voltage levels: Voltage level in RS-232 ranges from -25V to +25V. Voltage levels are categorized as signal voltage and control voltage.

Signal voltage between -3V to -25V represents logic “0,” while signal voltage between +3V to +25V represents logic “1.” On the contrary, the control voltage between -3V to -25V represents logic “1” while signal voltage between +3V to +25V represents logic “0.” Voltage between -3V to +3V is considered to be indeterminate.

      1. Slew rate: Slew rate is the rate of change of signal levels. (Read more...)

*** This is a Security Bloggers Network syndicated blog from Infosec Resources authored by Nitesh Malviya. Read the original post at: http://feedproxy.google.com/~r/infosecResources/~3/NpkCKiYGcvk/