DFE-500TX Ethernet PC Card User's Guide
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).
