DFE-500TX Ethernet PC Card User's Guide
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The DFE-500TX Adapter does not support the 100Base-T4 subtype. To
provide compatibility in traditional 10Mbps Ethernet environments (where, for
example, DFE-500TX adapters are installed
anticipating
upgrade of supporting
hub equipment to Fast Ethernet), the DFE-500TX also supports traditional
10Mbps Ethernet operation, in full-duplex as well as half-duplex modes.
Selection of the best operation mode in any given installation is automatically
governed by Autonegotiation.
About Autonegotiation
You have probably had the experience of making a dialup connection through a
modem, and have heard the gravelly
−
sounding exchanges between your
modem and the modem at the other end of the telephone line (these exchanges
are ordinarily played out through a speaker in your local modem). As irritating
as those few seconds of noise may be, they do let you know that your modem
and the remote modem are on the job, preparing for your intended
communication with the remote computer.
The preparatory work of the two modems during those few seconds before you
see the “connect” message is to
negotiate
the best data communication scheme
which is supported by both modems, and which is suitable for the quality of the
telephone line linkage between them. The parameters to be settled between the
two modems include best baud rate, compression method, and error correction
method. When the two modems have tested the phone-line quality and settled
on the combination of shared options and parameters which will provide the
best data communication over the connecting phone line, then you are given
the “connect” message which signals the end of the intermodem negotiation
and the beginning of your intended communication with the remote computer.
Autonegotiation between devices within an Ethernet LAN is similar in concept,
but much briefer. The two devices involved in the Autonegotiation will be the
DFE-500TX Adapter serving your station (
installed in your computer
), and the
hub through which it is connected into the LAN. The options to be negotiated
between the DFE-500TX and its supporting hub include Ethernet type
(100BASE-TX Fast Ethernet or 10BASE-T Ethernet) and duplex mode (half-
duplex, being one-way-at-a-time, or full duplex, being simultaneous transmit-
and-receive).
