PIC 16F877, 18F452 and 18F4550

There are many serial communication methods for example RS232, RS422, RS423 and RS485. Serial communication is used between computers and devices. The most widely used Serial communication method between two computers or from one computer and a device or even between two devices may be two micro controller or a PLC and display unit is RS232 and one main problem with RS232 interface is its length limitations.
When we want to communicate serially with larger distance then we use alternate methods like RS422, RS423 and RS485.
RS485 is the most versatile communication standard in the standard series defined by the EIA.
A comparison of Data communication on distance (lenght) is as under:
RS232 = 15 m maximum distance of communication.
RS423 and RS485 = 1200 m maximum distance of communication.

RS485 method uses some special devices for communication and main difference from rs232 interface is that, rs585 uses differential voltages between electric lines whereas rs232 uses level of voltages. Noise effect on rs485 is very low because of use of differentail voltages method and use of twisted pair of cables.

Labels: advantages of rs485 interface, alternate method of rs232, differentail voltages, high speed serial communicataion, length limitation, maximum distance is 1200m, noise effect, RS232, rs422, rs423, rs485