3X38FTR Datasheet, PDF (36/64 Pages) Agere Systems – OCTAL-FET (Fast Ethernet Transceiver) for 10Base-T/100Base-TX/FX

3X38FTR 208-Pin SQFP
OCTAL-FET for 10Base-T/100Base-TX/FX
Preliminary Data Sheet
September 2000
Functional Description (continued)
Bad SSD Detection
A bad start-of-stream delimiter (bad SSD) is an error
condition that occurs in the 100Base-X receiver if car-
rier is detected (CRS asserted) and a valid /J/K set of
code-groups (SSD) is not received.
If this condition is detected, then the 3X38 will assert
RXER and present RXD[3:0] = 1110 to the internal MII
for the cycles that correspond to received 5B code-
groups until at least two IDLE code-groups are
detected. In addition, the false carrier counter will be
incremented by one. Once at least two IDLE code
groups are detected, RXER and CRS become deas-
serted.
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. Since
autonegotiation is not currently specified for operation
over fiber, the far-end fault indication function (FEFI)
provides 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 1 of register 29. 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 3X38 will halt all current operations and
transmit the FEFI IDLE pattern when FOSD signal is
deasserted following a good link indication from the link
integrity monitor. If three or more FEFI IDLE patterns
are detected by the 3X38, then bit 4 of the basic mode
status register (address 01) is set to one until read by
management. Additionally, upon detection of far-end
fault, all receive and transmit MII activity is disabled/
ignored.
Carrier Integrity Monitor
The carrier integrity monitor (CIM) function protects the
repeater from transient conditions that would otherwise
cause spurious transmission due to a faulty link. This
function is required for repeater applications and is not
specified for switch applications.
The CIM function is controlled by bit 3 of register 29. It
is initialized to 1 (enabled) during powerup or reset. If
the CIM determines that the link is unstable, the 3X38
will not propagate the received data or control signaling
to the MII and will ignore data transmitted via the MII.
The 3X38 will continue to monitor the receive stream
for valid carrier events. The false carrier counter incre-
ments each time the link is unstable (bad SSD). Two
back-to-back false carrier events will isolate the PHY,
incrementing the associated isolate counter. Register
21 provides counters of carrier integrity events when
register 20, bit 11 is written to a 1 (the FIFO is in 32-bit
mode).
100Base-TX Transceiver
3X38 implements a TP-PMD compliant transceiver for
100Base-TX operation. The differential transmit driver
is shared by the 10Base-T and 100Base-TX sub-
systems. 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 3X38 100Base-TX transmit driver implements 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 stan-
dard.
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 3X38 uses an adaptive equalizer which changes
equalizer frequency response in accordance with cable
length. The cable length is estimated based on the
incoming signal behavior. The equalizer tunes itself
automatically for any cable length to compensate for
the amplitude and phase distortions incurred from the
cable.
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Lucent Technologies Inc.