Return to rs-232 CVS log

Up to [MW Coherent from dump] / coherent / a / usr / man / COHERENT

coherent

RS-232                Technical Information                RS-232




COM port wiring


This article  details the  connections (pinouts) of  EIA standard
RS-232C.  This  connect 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, DDTTEE stands  for ``data terminal
equipment'' and refers to terminal-type equipment such as a PC or
a  terminal,   whereas  DDCCEE  stands   for  ``data  communications
equipment'' and refers to modems and modem-type equipment.

_D_B-_2_5 _D_B-_9 _C_o_m_m_o_n
_P_i_n # _P_i_n #_N_a_m_e   _E_I_A _C_C_I_T_T_D_T_E-_D_C_E _D_e_s_c_r_i_p_t_i_o_n
  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


COHERENT Lexicon                                           Page 1




RS-232                Technical Information                RS-232



  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 *****

/uussrr/ppuubb/rrss223322 -- On-line version of above table

***** See Also *****

tteecchhnniiccaall iinnffoorrmmaattiioonn, tteerrmmiinnaall

Seyer,  M.D.: _R_S-_2_3_2 _M_a_d_e  _E_a_s_y: _C_o_n_n_e_c_t_i_n_g  _C_o_m_p_u_t_e_r_s, _P_r_i_n_t_e_r_s,
_T_e_r_m_i_n_a_l_s, _a_n_d _M_o_d_e_m_s.  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 considered  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!






























COHERENT Lexicon                                           Page 2

This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.