LU3X34FTR Datasheet, PDF (24/52 Pages) Agere Systems – Quad 3 V 10/100 Ethernet Transceiver TX/FX

LU3X34FTR
Quad 3 V 10/100 Ethernet Transceiver TX/FX
Preliminary Data Sheet
July 2000
Functional Description (continued)
Far-End Fault Indication
Autonegotiation provides a mechanism for transferring
information from the local station to the link partner that
a remote fault has occurred for 100Base-TX. As auto-
negotiation is not currently specified for operation over
fiber, the far-end fault indication function (FEFI) pro-
vides this capability for 100Base-FX applications.
A remote fault is an error in the link that one station can
detect while the other cannot. An example of this is a
disconnected wire at a station’s transmitter. This station
will be receiving valid data and detect that the link is
good via the link integrity monitor, but will not be able to
detect that its transmission is not propagating to the
other station.
A 100Base-FX station that detects such a remote fault
may modify its transmitted idle stream from all ones to
a group of 84 ones followed by a single 0. This is
referred to as the FEFI idle pattern.
The FEFI function is controlled by bit 11 of register 18h.
It is initialized to 1 (enabled) if the FOSEL pin is at logic
high level during powerup or reset. If the FEFI function
is enabled, the LU3X34FTR will halt all current opera-
tions and transmit the FEFI idle pattern when FOSD
signal is deasserted following a good link indication
from the link integrity monitor. FOSD signal is gener-
ated internally from the FORX± circuit. Transmission of
the FEFI idle pattern will continue until FORX± signal is
asserted. If three or more FEFI idle patterns are
detected by the LU3X34FTR, then bit 4 of the basic
mode status register (address 01h) is set to one until
read by management. Additionally, upon detection of
far-end fault, all receive and transmit MII activity is dis-
abled/ignored.
100Base-TX Transceiver
LU3X34FTR implements a TP-PMD compliant trans-
ceiver for 100Base-TX operation. The differential trans-
mit driver is shared by the 10Base-T and 100Base-TX
subsystems. This arrangement results in one device
that uses the same external magnetics for both the
10Base-T and the 100Base-TX transmission with sim-
ple RC component connections. The individually wave-
shaped 10Base-T and 100Base-TX transmit signals
are multiplexed in the transmit output driver section.
Transmit Drivers
The LU3X34FTR 100Base-TX transmit driver imple-
ments MLT-3 translation and wave-shaping functions.
The rise/fall time of the output signal is closely con-
trolled to conform to the target range specified in the
ANSI TP-PMD standard.
Twisted-Pair Receiver
For 100Base-TX operation, the incoming signal is
detected by the on-chip twisted-pair receiver that com-
prises the differential line receiver, an adaptive equal-
izer, and baseline wander compensation circuits.
The LU3X34FTR uses an adaptive equalizer which
changes filter frequency response in accordance with
cable length. The cable length is estimated based on
the incoming signal strength. The equalizer tunes itself
automatically for any cable length to compensate for
the amplitude and phase distortions incurred from the
cable.
24
Lucent Technologies Inc.