At 16:04 12/08/1999 , Byron A Jeff wrote: > > > > How about CSMA/CD? > >It's not clear if the physical layer of RS-485 allows for multiple >transmitters >or what happens if multiple transmitters transmit different bits. > >Essentially I'm doing the multiple access part because even with ethernet >there >is only a single transmitter on the channel at any point in time. This >protocol >handles channel selection on a separate channel using TDM on the slot channel. >So there are no collisions because there is guranteed not to be multiple >transmitters. > >I guess it would be possible to implement an ethernet type collision >detector on the second channel if RS-485 allows for multiple transmitters... You could steal the CAN bus method where a priority mechanism kicks in giving the bus to the higher priority message. >Any commentary on the UDP/SLIP part of it? The responses I've seen have been >physical layer only which isn't a relavent as the protocols on top of that I am implementing IP at the lowest layer, and TCP / UDP on top. May well dispense with TCP or use a highly cut down version. Intended to use PPP on top of that but memory constraints ... Check out Guy Lancaster's uCIP, TCP/IP/PPP for use with uCOS. www.ucos-ii.com. There's a listserver for it too. Regards Adrian --- WWW WWW Adrian Gothard WWW WW WWW White Horse Design WWWWWWWWWW +44-385-970009 (Mobile/SMS), +44-118-962-8913/4 (voice/fax) WWWW WWWW whd@zetnet.co.uk, http://www.users.zetnet.co.uk/whd --- Developers of GPS satellite-based tracking systems for vehicles/helicopters