STE10A datasheet(22/82 Pages) STMICROELECTRONICS

22 / 82 page

Functional description

STE10/100A

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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.

STE10A Datenblatt(PDF) 22 Page - STMicroelectronics