100BASE-TX Link Integrity Test

The Fast Ethernet transceiver circuits (PHY) continually monitor the receive data path for activity as a means of checking that the link is working correctly. The signalling system used for 100BASE-TX segments is based on the ANSI FDDI signalling system, which sends signals continually, even during idle periods of no network traffic. Therefore, activity on the receive data path is sufficient to provide a continual check of link integrity.

Nonetheless, 100BASE-TX twisted-pair transceivers that use 8-pin MDI connectors also send and receive link pulses. These pulses are called Fast Link Pulses, and they are used in the Auto-Negotiation mechanism which allows a multi-speed hub to detect the speed of operation of an Ethernet device that is connected to it, and to adjust the speed of the hub ports accordingly. Auto-Negotiation is described in Chapter 13.

Quick Reference Guide to 100BASE-TX - 09 SEP 95

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