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RS-485 Termination
Because each differential pair of wires is a transmission line, you must
properly terminate the line to prevent reflections. A common method of
terminating a two-wire multidrop RS-485 network is to install terminating
resistors at each end of the multidrop network. If you daisy-chained
multiple instruments together, you need a terminating resistor at only the
first and last instruments. The terminating resistor should match the
characteristic impedance of the transmission line (typically 100 to 120 ).
You can order an optional DB-9 RS-485 termination connector that
contains embedded terminating resistors for easy termination from
National Instruments. For ordering information, contact National
Instruments.
The following figure shows a multidrop network using terminating
resistors.
Multidrop Network Using Terminating Resistors
The following figure shows a full-duplex network using terminating
resistors.
Full-Duplex Network Using Terminating Resistors
Summary of Contents for ENET-232 Series
Page 1: ......
Page 5: ...Using Help Conventions Navigating Help Searching Help Printing Help File Topics ...
Page 21: ...Serial Hardware Overview PCI Kits PXI Kits USB Kits ENET Kits ExpressCard Kits PCMCIA Kits ...
Page 24: ...PCI 485I RS 485 two port isolated RS 485 four port isolated ...
Page 27: ...PXI 8423 RS 485 two port isolated RS 485 four port isolated ...
Page 63: ...Save Pending Changes To save your changes to this item click Save ...
Page 98: ...0 LPVOID l_SerialInterface sizeof l_SerialInterface LPDWORD l_ByteCount NULL ...
Page 127: ...2 PORT LEDs USB Serial Hardware LEDs ...
Page 139: ...Connecting the Cables to a Four Port PXI Serial Board ...
Page 141: ...67 58 50 41 33 24 16 7 TXD 9 RI 9 ...
Page 167: ......
Page 169: ......
Page 171: ......
Page 181: ...How many serial ports can I have on my machine You can have up to 256 serial ports ...
Page 201: ...Glossary Prefixes Symbols A B C D E F G H I K L M P R S T U V ...
Page 203: ...Symbols degrees ohms percent ...
Page 204: ...A A amperes ANSI American National Standards Institute ...
Page 205: ...B b bits B bytes baud bits per second bps bits per second ...
Page 208: ...E EIA Electronic Industries Association EMI electromagnetic interference ENET Ethernet ...
Page 209: ...F FCC Federal Communications Commission FIFO First In First Out ft feet ...
Page 210: ...G G ground ...
Page 211: ...H HSI handshake input HSO handshake output Hz Hertz ...
Page 213: ...K Kbaud kilobits per second ...
Page 214: ...L LED light emitting diode ...
Page 215: ...M m meters MB megabyte ...
Page 216: ...P PC personal computer PCI Peripheral Components Interconnect ...
Page 218: ...S s seconds SCSI Small Computer Systems Interface ...
Page 220: ...U UART Universal Asynchronous Receiver Transmitter ...
Page 221: ...V V volts VDC volts direct current VXI VME eXtensions for Instrumentation ...