User`s manual

8 Serial Port I/O
8-6
If you connect two DTE’s or two DCE’s using a straight serial cable, then the
TD pin on each device are connected to each other, and the RD pin on each
device are connected to each other. Therefore, to connect two like devices, you
must use a null modem cable. As shown below, null modem cables cross the
transmit and receive lines in the cable.
Note You can connect multiple RS-422 or RS-485 devices to a serial port. If
you have an RS-232/RS-485 adaptor, then you can use MATLAB’s serial port
object with these devices.
Serial Port Signals and Pin Assignments
Serial ports consist of two signal types: data signals and control signals. To
support these signal types, as well as the signal ground, the RS-232 standard
defines a 25-pin connection. However, most PC’s and UNIX platforms use a
9-pin connection. In fact, only three pins are required for serial port
communications: one for receiving data, one for transmitting data, and one for
the signal ground.
DTE
DTE
TD
Pin 2
Pin 3
Pin 2
Pin 3
TD
RDRD
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