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
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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.