COHERENT manpages
This page displays the COHERENT manpage for RS-232 [Serial port wiring].
List of available manpages
Index
RS-232 -- Technical Information Serial port wiring This article details the connections (pinouts) of EIA standard RS-232C. This connector consists of a D-shaped plug with 25 pins in two rows: 13 pins in the upper row and 12 in the lower. This interface is commonly used by devices that require a serial interface to a computer; these devices include modems, terminals, serial printers, and such specialized devices as bar-code scanners. In addition, this articles gives the pinouts of the nine-pin DB-9P connector, which is a nine-pin version of the RS-232 that is commonly used in AT and AT-compatible computers. RS-232 Pinout The following table gives the 25-pin EIA standard RS-232C pinouts. It also gives: -> Nine-pin DB-9P convention -> Common abbreviations of signal names -> Abbreviations of RS-232 signal names -> Equivalent CCITT signal-number designations -> Signal direction (as appropriate) -> Signal description Please note that in this table, DTE stands for ``data terminal equipment'' and refers to terminal-type equipment such as a PC or a terminal, whereas DCE stands for ``data communications equipment'' and refers to modems and modem-type equipment. DB-25 DB-9 Common Pin # Pin #Name EIA CCITTDTE-DCE Description 1 FG AA 101 -- Frame ground 2 3 TD BA 103 -> Transmitted data 3 2 RD BB 104 <- Received data 4 7 RTS CA 105 -> Request to send 5 8 CTS CB 106 <- Clear to send 6 6 DSR CC 107 <- Data set ready 7 5 SG AB 102 -- Signal ground 8 1 DCD CF 109 <- Data carrier detect 9 -- -- -- -- Positive DC test voltage 10 -- -- -- -- Negative DC test voltage 11 QM -- -- <- Equalizer mode 12 SDCD SCF 122 <- Secondary carrier detect 13 SCTS SCB 121 <- Secondary clear to send 14 STD SBA 118 -> Secondary transmitted data 15 TC DB 114 <- Transmitter clock 16 SRD SBB 119 <- Secondary receiver clock 17 RC DD 115 -> Receiver clock 18 DCR -- -- <- Divided clock receiver 19 SRTS SCA 120 -> Secondary request to send 20 4 DTR CD 108.2 -> Data terminal ready 21 SQ CG 110 <- Signal quality 22 9 RI CE 125 <- Ring indicator 23 -- CH 111 -> Data rate selector 24 TC DA 113 <- Transmitted clock 25 Files /usr/pub/rs232 -- On-line version of above table See Also Administering COHERENT, asy, modem, terminal Seyer, M.D.: RS-232 Made Easy: Connecting Computers, Printers, Terminals, and Modems. Englewood Cliffs, NJ, Prentice-Hall Inc., 1984. Notes Serial ports on the back of the PC use either a 25-pin male (DB-25P) or a nine-pin male (DB-9P) connector. Due to what can only be regarded as extreme stupidity, the 25-pin female (DB-25S) connector was chosen for the parallel (printer) port, rather than using the usual 36-pin parallel connector. Do not confuse these ports when wiring custom-cable assemblies, as you can damage your equipment!