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Cabling
The computer’s RS-232-C serial port is an IBM PC style serial interface. It has an IBM PC
AT, D-shell, male connector. This connector has 9 pins instead of the conventional 25 pins.
To connect any serial device to the computer, you need the same cable that you would use to
connect that device to an IBM PC XT. Your dealer should be able to provide this type of
cable. If you can’t get an IBM PC XT style cable, you may need to have a custom made
cable.
The pin assignments for the computer serial port are:
Pin Signal I/O Description
1 DCD I Data carrier detect
2 RD I Serial receive data
3 SD O Serial transmit data
4 DTR O Data terminal ready
5 GND Signal ground (0 V)
6 DSR I Data set ready
7 RTS O Request to send
8 CTS I Clear to send
9 RI I Ring indicator
Communication Settings
There are other considerations in serial communications. They include:
The computer’s internal configuration. (MS-DOS must know which logical serial port,
COM1 or COM2, should receive and send data.)
The internal configuration of the peripheral device.