National Instruments ENET-232 Series, Manual

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PCMCIA Kits
The PCMCIA serial hardware gives you a variety of solutions for serial
communication. The PCMCIA-232 interfaces work with the RS-232
protocol, and the PCMCIA-485 interfaces work with the RS-422 and RS-
485 protocols. You can use the RS-232 ports for serial communication up
to distances of 50 ft. You can connect the RS-485 ports to up to 31
devices using serial cable lengths up to 4,000 ft.
The PCMCIA-232 is available in one-port, two-port, and four-port
versions. The PCMCIA-485 is available in one-port or two-port versions.
All PCMCIA cards come with cables for each port that terminates in a
standard DB-9 connector. Throughout this help file,
PCMCIA serial
interfaces refers to all versions of the interfaces.
The RS-232 ports are DTE. In the RS-232 specification, Data Terminal
Equipment (DTE) and Data Communications Equipment (DCE) 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.
For more information about cabling a RS-232 port to other devices, refer
to
RS-232 DTE vs. DCE .
The RS-485 ports support four hardware transceiver control modes for
reliable communication with two and four-wire devices. For more
information about transceiver control modes, refer to
RS-485 Transceiver
Control .
All PCMCIA serial hardware uses standard 16550-compatible UARTs
(Universal Asynchronous Receiver/Transmitters) for complete
compatibility with standard PC COM ports. The serial hardware contains
FIFO (First-In-First-Out) buffers to reduce susceptibility to interrupt
latency for faster transmission rates. Full Plug and Play compatibility
allows switchless configuration and installation. For more information
about the serial hardware specifications and operating conditions, refer to
the
NI Serial Hardware Guide .