STE10 Datasheet, PDF (50/66 Pages) STMicroelectronics – PCI 10/100 ETHERNET CONTROLLER WITH INTEGRATED PHY 5V

STE10/100
6.5.2 Transceiver Operation
The transceiver portion of the STE10/100 integrates the IEEE802.3u compliant functions of PCS (physical cod-
ing sub-layer), PMA (physical medium attachment) sub-layer, and PMD (physical medium dependent) sub-layer
for 100BASE-TX, and the IEEE802.3 compliant functions of Manchester encoding/decoding and transceiver for
10BASE-T. All the functions and operating schemes are described in the following sections.
s 100BASE-TX Transmit Operation
For 100BASE-TX transmissions, the STE10/100 transceiver provides the transmission functions of
PCS, PMA, and PMD for encoding of MII data nibbles into five-bit code-groups (4B/5B), scrambling,
serialization of scrambled code-groups, converting the serial NRZ code into NRZI code, converting the
NRZI code into MLT3 code, and then driving the MLT3 code into the category 5 Unshielded Twisted
Pair cable through an isolation transformer with the turns ratio of 1.414 : 1.
s Data code-groups Encoder: In normal MII mode applications, the transceiver receives nibble type 4B
data via the TxD0~3 inputs of the MII. These inputs are sampled by the transceiver on the rising edge
of Tx-clk and passed to the 4B/5B encoder to generate the 5B code-group used by 100BASE-TX.
s Idle code-groups: In order to establish and maintain the clock synchronization, the transceiver must
keep transmitting signals to medium. The transceiver will generate Idle code-groups for transmission
when there is no actual data to be sent by MAC.
s Start-of-Stream Delimiter-SSD (/J/K/): In a transmission stream, the first 16 nibbles comprise the
MAC preamble. In order to let a network partner delineate the boundary of a data transmission
sequence and to authenticate carrier events, the transceiver will replace the first 2 nibbles of the MAC
preamble with /J/K/ code-groups.
s 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.
s 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.
s 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.
s 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.
s 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.
s 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
50/66