Hi All
I have never worked on RS422. As programming point of view is there any difference between serial port RS232 & RS422.Ya hardware level i know

http://digital.ni.com/public.nsf/all...256F1D005AD0CD

But do we use same api's for RS422 as what we use for RS232 ?

Yes, there is no programming difference between RS-232 and RS-422.

Since you've chosen to pose a software question about a hardware standard, the answer is 'Yes, and No'. Since RS-422 is a multidrop protocol, there is very often a software level protocol added to determine which node is allowed to talk at any instant. Also, there is probably some need to deal with addressing, so node-specific data can be directed to specific nodes.
In Linux, it is quite likely that the standard termios API and UART drivers will work with a RS-422 interface. It depends on the hardware implementation, which almost always uses RS-232 compatible UARTs.

--- rod.