National Instruments ENET-232 Series, Manual

Page: 29 / 237

ENET Kits
The ENET serial hardware gives you a variety of solutions for serial
communication. The RS-232 interfaces work with the RS-232 protocols.
The RS-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 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 boards 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 serial ENET interfaces contain FIFO (First-In-First-Out) buffers to
reduce susceptibility to interrupt latency for faster transmission rates.
Also, serial ENET interfaces contain additional onboard buffers to reduce
susceptibility to Ethernet network traffic.
With a serial ENET interface, you gain all the features inherent in a
networked device: fewer cabling distance restrictions, device sharing,
and communication with devices throughout the Internet. In a serial
application, you usually are restricted to the distance limitations of the
RS-232, RS-422, or RS-485 specifications. Because the serial ENET
interface uses Ethernet, you can add an unlimited distance to your
application by exploiting the distances available using a networked
device. Device sharing with a serial ENET interface happens on a per-
port basis. That is, although the serial ENET interface supports network
connections from multiple hosts, each serial port is associated with only
one host at a time.
Dynamic Host Configuration Protocol (DHCP) is available on many
networks to configure network parameters automatically. DHCP simplifies
the installation and configuration process for the serial ENET. For more
information about DHCP, refer to
Using DHCP .