I need an RS-232 port to run at 230.4 kbps or higher. What are my options?
On purely technical merits, RS-422 is the best choice for the physical layer. You get lower noise emissions, +/-7V of common-mode voltage range, and enough bandwidth to handle X2 and ADSL modems. TIA/EIA-644 (LVDS) offers many of the same features as RS-422 with an easy integration path but with less common-mode voltage range. There are various standard interfaces already defined and in use that employ RS-422 signaling, none in the PC world however. Market-wise, you’ve got billions and billions (well, maybe 100’s of millions) of DB25 and DB9 connectors on the backs of PC’s that use RS-232. To that end, TIA/EIA-694 was developed in TR30.2 and is now a published standard. It basically takes RS-232 up to 512 kbps and maintains mechanical and electrical compatibility with all the older RS-232 versions. The concept is for the modem and PC supplier to have a RS-232/694-512 or -115 or -230 or -345 labeled port depending upon what speed the UART and line circuits will support. Serial communica
