STE10A Datasheet, PDF (24/82 Pages) STMicroelectronics – PCI 10/100 Ethernet controller with integrated PHY (3.3V)

Functional description
STE10/100A
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.
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