STE100A datasheet(24/82 Pages) STMICROELECTRONICS

24 / 82 page

Functional description

STE10/100A

24/82

Full duplex and half duplex operation of transceiver

The transceiver can operate in either full duplex or half duplex network applications. In full

duplex, both transmission and reception can take place simultaneously. In full duplex mode,

collision (COL) signal is ignored and carrier sense (CRS) signal is asserted only when the

transceiver is receiving.

In half duplex mode, transmission and reception can not take place simultaneously. In half

duplex mode, the collision signal is asserted when transmitted and received signals collide,

and carrier sense is asserted during both transmission and reception.

Auto-negotiation operation

The auto-negotiation function provides the means to exchange information between the

transceiver and the network partner to automatically configure both to take maximum

advantage of their abilities. The auto-negotiation function is controlled by ANEN (bit 12 of

XR0).

During auto-negotiation information is exchanged with the network partner using fast link

pulses (FLPs) - a burst of link pulses. There are 16 bits of signaling information contained in

the link pulses which advertise to the remote partner the capabilities which are represented

by the contents of ANA (register XR4). According to this information the partners find out

their highest common capabilities by following the priority sequence listed below:

–

100BASE-TX full duplex

–

100BASE-TX half duplex

–

10BASE-T full duplex

–

10BASE-T half duplex

During power-up or reset, if auto-negotiation is enabled, the FLPs will be transmitted and

the auto-negotiation function will proceed. Otherwise, auto-negotiation will not occur until

ANEN (bit 12 of XR0) is set to 1. When the auto-negotiation is disabled, then network speed

and duplex mode are selected by programming the XR0 register.

Power down operation

The transceiver is designed with a power-down feature which can reduce power

consumption significantly. Since the power supply of the 100BASE-TX and 10BASE-T

circuits are separate, the transceiver can turn off the circuit of either the 100BASE-TX or

10BASE-T when the other is active.

STE100A датащи(PDF) 24 Page - STMicroelectronics