STE10A Datasheet, PDF (22/82 Pages) STMicroelectronics – PCI 10/100 Ethernet controller with integrated PHY (3.3V)

Functional description
STE10/100A
End-of-stream delimiter-ESD (/T/R/)
In order to indicate the termination of normal data transmissions, the transceiver will insert 2
nibbles of /T/R/ code-group after the last nibble of the FCS.
Scrambling
All the encoded data (including the idle, SSD, and ESD code-groups) is passed to the data
scrambler to reduce EMI by spreading the power spectrum using a 10-bit scrambler seed
loaded at the beginning.
Data conversion of parallel to serial, NRZ to NRZI, NRZI to MLT3
After being scrambled, the 5B type transmission data at 25MHz will be converted to a
125HMz serial bit stream by the parallel-to-serial function. The bit stream will be further
converted from NRZ to NRZI format, unless the conversion function is bypassed by clearing
ENRZI (bit 7 of XR10) to 0. After NRZI conversion, the NRZI bit stream is passed through
MLT3 encoder to generate the TP-PMD specified MLT3 code. By using MLT3 code, the
frequency and energy content of the transmission signal is reduced in the UTP, making the
system more easily compliant to FCC EMI specifications.
Wave-shaper and media signal driver
In order to reduce the energy of the harmonic frequency of transmission signals, the
transceiver provides a wave-shaper prior the line driver to smooth the rising/falling edge of
transmission signals while maintaining the waveforms’ symmetry. The 100BASE-TX and
10BASE-T wave-shaped signals are both passed to the same media signal driver. This can
simplify system design by employing a single external magnetic connection.
100BASE-TX receiving operation
For 100BASE-TX receiving operation, the transceiver provides the receiving functions of
PMD, PMA, and PCS for incoming data signals through category 5 UTP cable and an
isolation transformer with a 1:1 turns ratio. The receive transceiver portion includes the
adaptive equalizer and baseline wander, MLT3 to NRZI data conversion, NRZI to NRZ
conversion, serial to parallel conversion, a PLL for clock and data recovery, de-scrambler,
and the 5B/4B decoder.
Adaptive equalizer and baseline wander
High speed signals over unshielded (or shielded) twisted pair cable will experience
attenuation and phase shift. These effects depend on the signal frequency, cable type, cable
length and the cable connectors. Robust circuits in the transceiver provide reliable adaptive
equalizer and baseline wander compensation for amplitude attenuation and phase shift due
to transmission line parasites.
MLT3 to NRZI decoder and PLL for data recovery
Following adaptive equalizer, baseline wander, the transceiver converts the resulting MLT3
to NRZI code, which is passed to the Phase Lock Loop circuits in order to extract the
synchronous clock and the original data.
22/82