PC RS-232 Com Port Connector

The table below shows the most commonly implemented signals and their pin assignments in accordance with RS-232D. Host computers are usually DTE (Data Terminal Equipment) and modems are DCE (Data Communications Equipment). Note that circuits are named from the point of view of the DTE. For example, circuit BB (receive data) is actually data transmitted by the DCE. DCE devices normally use a 25 pin, female, D connector.

     Pin   Circuit   Description                 Direction
     --------------------------------------------------------------
      1     AA       Protective ground, PG       n/a
      2     BA       Transmit data, TD           to DCE
      3     BB       Receive data, RD            from DCE
      4     CA       Request to send, RTS        to DCE
      5     CB       Clear to send, CTS          from DCE
      6     CC       Data set ready, DSR         from DCE
      7     AB       Signal ground, SG           n/a
      8     CF       Data carrier detect, DCD    from DCE
     20     CD       Data Terminal ready, DTR    to DCE
     22     CE       Ring indicator, RI          from DCE
Many IBM's and compatibles use a 9 pin, male, D connector instead of the 25 pin connector. The pin assignments for such a DTE device are shown below.
     Pin   Circuit   Description                 Direction
     --------------------------------------------------------------
      1     CF       Data carrier detect, DCD    from DCE
      2     BB       Receive data, RD            from DCE
      3     BA       Transmit data, TD           to DCE
      4     CD       Data Terminal ready, DTR    to DCE
      5     AB       Signal ground, SG           n/a
      6     CC       Data set ready, DSR         from DCE
      7     CA       Request to send, RTS        to DCE
      8     CB       Clear to send, CTS          from DCE
      9     CE       Ring indicator, RI          from DCE
All Lucid Technologies programmers are designed as DCE devices. They use a 9 pin, female, D connector that is directly compatible with 9 pin COM ports found on most IBM compatibles.
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