Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!rutgers!topaz.rutgers.edu!ron From: ron@topaz.rutgers.edu (Ron Natalie) Newsgroups: comp.emacs Subject: Re: 9600 baud problems (was Re: when using termcap, get it right!) Message-ID: <13403@topaz.rutgers.edu> Date: Mon, 20-Jul-87 17:30:04 EDT Article-I.D.: topaz.13403 Posted: Mon Jul 20 17:30:04 1987 Date-Received: Wed, 22-Jul-87 00:45:24 EDT References: <1373@bobkat.UUCP> <8707061522.AA07395@ucbvax.Berkeley.EDU> <14358@teknowledge-vaxc.ARPA> Organization: Rutgers Univ., New Brunswick, N.J. Lines: 43 A quick summary of RS-232C The world is divided into DTE and DCE. DTE is data terminal equipment, sometimes referred to as the business machine. This includes what we refer to as terminals as well as the computers. DTE's SHOULD have male DB-25's on them. DCE is the communications network end. Modems fall into this category. DCE should correspondingly have the female DB-25 connector. Here are the popular signals. Note the letters DCE or DTE indicate whether the signal is sourced from the communications equipment or terminal equipment respectively: DSR (Data Set Ready)-DCE- I am up and running and ready to place/receive calls. Should remain on whenever the DCE is on and happy. DTR (Data Terminal Ready) -DTE- I am ready to receive calls. While many people use this to indicate that they are ready and assert it all the time when they are up (which is legal), a terminal is allowed to wait until the RI line comes up before raising DTR. Once raised, it should never be lowered unless you wish to sever the connection. RI (Ring Indicator) -DCE- The phone is ringing, there is a call pending... CD (Carrier Detect), also refered to as RLSD (Recieve Line Signal Detect?) -DCE- I have detected a valid signal from the remote modem. RTS (Request to Send) -DTE- Generally ignored in the full-duplex world, but this is asserted when the terminal wants to send data to the DCE. In the half-duplex or multi-drop environment, the DCE must prepare itself to send the data. CTS (Clear to Send) -DCE- Answer to RTS. Terminal may send it's data now. and just for completeness TD (Transmit Data) -DTE- Data from terminal TO DCE RD (Recieve Data) -DCE- Data to DTE from DCE Note, that RS-232C has NO FLOW CONTROL. Let me say this again. THERE IS NO FLOW CONTROL. RS-232C describes the interconnection of a terminal with a modem. Some signals like TRANSMIT and RECEIVE DATA are passed through to the other side. Other signals may be affected by actions on the other side, but they are indications from the modem to the terminal specifically. RTS and CTS are properties of the transmission of DATA to the MODEM, these signals go no farther than the modem. The same for DTR, DSR, CD, and RI. If you are using RS-232, flow control needs to be done in the data stream. -Ron