host: elwood
path: /usr/local/database/faq/datalinks
file: rs_232.txt

M.Braun - MHE 1 - 21.02.00


Frequently asked Questions: RS 232 serial datalinks
---------------------------------------------------


Q: What are the pinouts of RS 232 connectors ?

A: RS 232 pinouts

   Input to the PC is usually via 9-pin male sockets. These have pinouts as
   follows:


   Abbreviations
   -------------
   DCD   Data Carrier Detect
   Rx    Receive Data
   Tx    Transmit Data
   DTR   Data Terminal ready
   GND   Ground
   DSR   Data Set Ready
   RTS   Request To Send
   CTS   Clear to Send
   RI    Ring Indicator

   NC    Not Connected

   +Tx   +Tx Data Current Loop
   -Tx   -Tx Data Current Loop
   +Rx   +Rx Data Current Loop
   -Rx   -Rx Data Current Loop

   <     Input
    >    Output


   9-way - male PC socket (cable requires female)
   ----------------------------------------------
    1  <   DCD
    2  <   Rx
    3   >  Tx
    4   >  DTR
    5      GND
    6  <   DSR
    7   >  RTS
    8  <   CTS
    9  <   RI


   25-way - male PC socket (cable requires female)
   -----------------------------------------------
    1      NC   (shield ground other end)
    2   >  Tx
    3  <   Rx
    4   >  RTS
    5  <   CTS
    6  <   DSR
    7      GND
    8  <   DCD
    9   >  +Tx
   10      NC
   11   >  -Tx
   12      NC
   13      NC
   14      NC
   15      NC
   16      NC
   17      NC
   18  <   +Rx
   19      NC
   20   >  DTR
   21      NC
   22  <   RI 
   23      NC
   24      NC
   25  <   -Rx


   9 - 25 Converter Plug
   ---------------------
   1    8  DCD
   2    3  Rx
   3    2  Tx
   4   20  DTR
   5    7  GND
   6    6  DSR
   7    4  RTS
   8    5  CTS
   9   22  RI


   9 - 25 Connection Cable (e.g. Workstation/Modem)
   ------------------------------------------------
   Rx   2  --\/--  2  Tx
   Tx   3  --/\--  3  Rx

   CTS  8  --\/--  4  RTS
   RTS  7  --/\--  5  CTS

   DTR  4  --\/--  6  DSR
   DSR  6  --/\-- 20  DTR

   DCD  1  ------  8  DCD
   RI   9  ------ 22  RI

   GND  5  ------  7  GND