STE10/100A
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6.5.2 Transceiver Operation
The transceiver portion of the STE10/100A integrates the IEEE802.3u compliant functions of PCS (physical
coding 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 trans-
ceiver for 10BASE-T. All the functions and operating schemes are described in the following sections.
■100BA SE-TX Tra nsmi t Opera tion
For 100BASE-TX transmission s, the STE 10/100A transce iver pr ov ide s th e tra ns mi ssion funct ion s of
PCS, PMA, and PMD for e ncoding of MII data nibbles into five-bi t code-groups (4B/5B), scram bling,
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 wit h the turns ratio of 1: 1.
■Recommended Transformers: HB626-1 from Transpower Technologies, 9410 Prototype Drive, Suite
#1, Reno, NV 89511. Tel: (775) 852-0140 and H1102 from Pulse Engineering Inc., 12220 World Trade
Drive, San Diego, CA92128. Tel: (619) 674-8100.
■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 gene rate the 5B code-group used by 100B ASE-TX .
■Idle c ode - gr o up s : In order to establish and maintain the clock synchronization, the transceiver must
keep transmitting signals to medium. The transceiver will generate Idle code-group s for transmission
when there is no actual data to be se nt by MAC.
■Start-of-Stream Delimite r-SSD (/J/K/): In a transmissio n stream, the first 16 nibb les comprise the
MAC preamble . In order to let a n etwo rk partner delineate the boundary of a data tr ansm ission
sequence and to authenticate carrier events, the transceiver will replace the first 2 nibbles of the MAC
preamble with /J/ K/ code-groups.
■End-of-Stream Delimiter- ESD (/T/R/): In order to indicat e 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 b eing scra mbled, the 5B
type transmission data at 25MHz will be converted to a 125HMz serial bit stream by the parallel-to-serial
fun c tio n . Th e bit s trea m w ill be f u rthe r c o nv e rted fro m NRZ to N RZI format, un les s the c o nv e rs io n
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-Sh ape r and Media Sign al 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-sh a ped signals are b oth passed to the same media signal driver. This can simplify
system design by employing a single external magnetic connection.
■100BA SE-TX Recei ving Op erati on
For 100BASE-T X 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 equal izer and baseline wand er,
MLT3 to NRZI data conversion, NRZI to NRZ conversion, serial to parallel conversion, a PLL for clock
and data recove ry, de-scramble r, and the 5B/4B decod er.
■Adaptive Equalizer and Baseline Wander: High speed signals over unshielded (or shielded) twisted