DFE-660TX Fast Ethernet PC Card User's Guide
Introduction
3
100Base-FX (using two fiber-optic strands).
The DFE-660TX provides half-duplex 100Base-TX operation (in
Category 5 twisted-pair cable environments). It does not provide
100Base-T4 or 100Base-FX operation. To provide for traditional
10Mbps Ethernet operation in twisted-pair cable environments, the
DFE-660TX also offers 10Mbps Ethernet operation, in full-duplex
and half-duplex modes. The DFE-660TX's autonegotiation
capability provides for automatic selection of the best operation
mode.
About Autonegotiation
The basic idea of autonegotiation can be understood by reflecting for
a moment on the familiar process of making a dialup connection
between two modems. You have probably heard some
gravelly
−
sounding exchanges between your local modem and a
modem at the other end of a 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 connection
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 have switched to the combination of parameters
which will provide the best data communication, then you are given
the “ connect” message which signals the end of the inter-modem
negotiation and the beginning of your intended communication with
the remote computer.
