
Lucent Technologies Inc.
21
Preliminary Data Sheet
July 2000
LU3X32FT Two-Port 3 V 10/100
Ethernet Transceiver TX/FX
Functional Description
(continued)
100Base-TX Transceiver
LU3X32FT implements TP-PMD compliant transceivers for 100Base-TX operation. The differential transmit 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 simple 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 LU3X32FT 100Base-TX transmit drivers implement MLT-3 translation and wave-shaping
functions. The rise/fall time of the output signal is closely controlled 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
receivers that comprise the differential line receiver, an adaptive equalizer, and baseline wander compensation cir-
cuits.
The LU3X32FT uses adaptive equalizers which change 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.
10Base-T Module
The 10Base-T transceiver modules are IEEE802.3 compliant. They include the receiver, transmitter, collision,
heartbeat, loopback, jabber, waveshaper, and link integrity functions, as defined in the standard. Figure 4 provides
an overview for the 10Base-T modules.
The LU3X32FT 10Base-T modules are comprised of the following functional blocks:
I
Manchester encoder and decoder
I
Collision detector
I
Link test function
I
Transmit driver and receiver
I
Serial and parallel interface
I
Jabber and SQE test functions
I
Polarity detection and correction
5-7910(F)
Figure 4. 10Base-T Module Data Path (per port)
TPRX±
RECEIVE
FILTER
FILTER
SMART
SQUELCH
CLOCK
RECOVERY
10BASE-T
RECEIVE
PCS
RXCLK
CRS
RXDV
RXD[3:0]
COL
10/100
TRANSMIT
DRIVER
WAVE
SHAPER
10BASE-T
TRANSMIT
PCS
TXEN
TXER
TXD[3:0]
TXCLK
TPTX±
10M PHY
LOOPBACK
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