Figure E-1. Male Db-9 Connector Pin Locations - National Instruments GPIB-232 User Manual

Appendix E Interfacing to an RS-485 Device
RS-485
Description of the RS-485 Port
GPIB-232/485CT-A User Manual
RS-485, as specified in the EIA-485 Standard, Standard for Electrical
Characteristics of Generators and Receivers for Use in Balanced Digital
Multipoint Systems, expands on the RS-422 standard by increasing the
number of devices you can use from 10 to 32 and by working with
half-duplex bus architectures. Unlike the RS-422 standard, RS-485
addresses the issue of using multiple transmitters on the same line. RS-485
defines the electrical characteristics necessary to ensure adequate signal
voltages under maximum load, short circuit protection, and the ability to
withstand multiple drivers driving conflicting signals at the same time.
The RS-485 serial port on the GPIB-485CT-A uses a male 9-pin
D-Subminiature connector. Figure E-1 shows the pin locations on the
connector. Table E-1 shows the signal lines supported on the
GPIB-485CT-A.
CTS–(HSI–)
RTS–(HSO–)

Figure E-1. Male DB-9 Connector Pin Locations

TXD+
TXD–
E-2
GND
CTS+(HSI+)
RTS+(HSO+)
RXD+
RXD–
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