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RS-232 DTE versus DCE
In the RS-232 specification, DTE (Data Terminal Equipment) and DCE
(Data Communications Equipment) refer to the types of equipment on
either end of a serial connection. In general, DTE and DCE refer to
computer equipment and modems, respectively. Because the RS-232
specification mainly involves connecting a DTE directly to a DCE and
vice versa, the pinouts are defined so that cabling is simple. That is, a
cable connected a computer to a modem by wiring pin 1 to pin 1, pin 2 to
pin 2, and so on. This method is known as
straight-through
cabling.
The following figure shows straight-through cabling in a DTE-to-DCE
interface.
Straight-Through Cabling in a DTE-to-DCE Interface
Straight-through cabling is still the standard method to connect a modem
to your PC. However, because many applications use serial
communication to connect two or more DTEs without modems, the
cabling becomes more complicated. If two DTEs are wired together using
a straight-through cable, one transmitter is connected to the other
transmitter, and one receiver is connected to the other receiver. In this
setup, no transmissions can occur. Thus, these applications must use a
cabling scheme that connects the transmitter on one device to the
receiver on the other device and vice versa. This method is known as
null-modem
cabling, because it replaces the two modems that traditional
RS-232 applications would require between the two DTEs. To
communicate from one DTE serial port to another, use a null-modem
cable.
The following figure shows null-modem cabling in a DTE-to-DTE
interface.
Null-Modem Cabling in a DTE-to-DTE Interface
PCI, PXI, USB (one port only), ENET, ExpressCard, and PCMCIA RS-
Содержание ENET-232 Series
Страница 1: ......
Страница 5: ...Using Help Conventions Navigating Help Searching Help Printing Help File Topics ...
Страница 17: ...How to Use this Help File To use this help file refer to the following flow chart and the appropriate topics ...
Страница 21: ...Serial Hardware Overview PCI Kits PXI Kits USB Kits ENET Kits ExpressCard Kits PCMCIA Kits ...
Страница 24: ...PCI 485I RS 485 two port isolated RS 485 four port isolated ...
Страница 27: ...PXI 8423 RS 485 two port isolated RS 485 four port isolated ...
Страница 63: ...Save Pending Changes To save your changes to this item click Save ...
Страница 65: ...Restore Defaults To reset the fields to their default values at any time click the Defaults button ...
Страница 98: ...0 LPVOID l_SerialInterface sizeof l_SerialInterface LPDWORD l_ByteCount NULL ...
Страница 127: ...2 PORT LEDs USB Serial Hardware LEDs ...
Страница 139: ...Connecting the Cables to a Four Port PXI Serial Board ...
Страница 141: ...67 58 50 41 33 24 16 7 TXD 9 RI 9 ...
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Страница 171: ......
Страница 181: ...How many serial ports can I have on my machine You can have up to 256 serial ports ...
Страница 189: ...nslookup hostname If you still cannot communicate with your device contact National Instruments ...
Страница 201: ...Glossary Prefixes Symbols A B C D E F G H I K L M P R S T U V ...
Страница 203: ...Symbols degrees ohms percent ...
Страница 204: ...A A amperes ANSI American National Standards Institute ...
Страница 205: ...B b bits B bytes baud bits per second bps bits per second ...
Страница 206: ...C C Celsius COM Computer Output Microform used in reference to a communication port CTS clear to send ...
Страница 208: ...E EIA Electronic Industries Association EMI electromagnetic interference ENET Ethernet ...
Страница 209: ...F FCC Federal Communications Commission FIFO First In First Out ft feet ...
Страница 210: ...G G ground ...
Страница 211: ...H HSI handshake input HSO handshake output Hz Hertz ...
Страница 213: ...K Kbaud kilobits per second ...
Страница 214: ...L LED light emitting diode ...
Страница 215: ...M m meters MB megabyte ...
Страница 216: ...P PC personal computer PCI Peripheral Components Interconnect ...
Страница 218: ...S s seconds SCSI Small Computer Systems Interface ...
Страница 220: ...U UART Universal Asynchronous Receiver Transmitter ...
Страница 221: ...V V volts VDC volts direct current VXI VME eXtensions for Instrumentation ...
Страница 222: ...Important Information Warranty Copyright Trademarks Patents Warning Regarding Use of NI Products Compliance ...