> I'd like to know what is the improvement > added in RS232C ? I've never seen revs A or B and can't be bothered digging out my spec for C. However, I do have to hand a book from a TI seminar I attended in 1993. It discusses changes to RS232 through revs C, D & E in reference to their line drivers. Actually, it was RS232 to Rev C and then EIA- 232 from then on. My summary - Rev C spec's a max cable length of 15m. Rev D & E changed that to a max capacitive load of 2500pF. Rev D imposed a maximum risetime through the transition region of 5us or 4% of the bittime. Rev E just says 4% of the bittime. There is a 30V/us max slewrate. The spec (up to & including E) limits datarate to 20kbps, but if you extrapolate the (Rev E) risetime limit to its intersection with the slewrate limit, you get a max datarate of 200kbps. (Sober) Steve ====================================================== Steve Baldwin Electronic Product Design TLA Microsystems Ltd Microcontroller Specialists PO Box 15-680, New Lynn http://www.tla.co.nz Auckland, New Zealand ph +64 9 820-2221 email: steveb@tla.co.nz fax +64 9 820-1929 ====================================================== -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body