I347-AT4 Datasheet, PDF (27/148 Pages) Intel Corporation – Intel® Ethernet Network Connection I347-AT4 Datasheet

Device Functionality—I347-AT4
3.2.1
Transmit Side Network Interface
3.2.1.1
Multi-mode TX Digital-to-Analog Converter
The I347-AT4 incorporates a multi-mode transmit DAC to generate filtered 4D PAM 5,
MLT3, or Manchester coded symbols. The transmit DAC performs signal wave shaping
to reduce EMI. The transmit DAC is designed for very low parasitic loading capacitances
to improve the return loss requirement, which allows the use of low cost transformers.
3.2.1.2
Slew Rate Control and Waveshaping
In 1000BASE-T mode, partial response filtering and slew rate control is used to
minimize high frequency EMI. In 100BASE-TX mode, slew rate control is used to
minimize high frequency EMI. In 10BASE-T mode, the output waveform is pre-
equalized via a digital filter.
3.2.2
Encoder
3.2.2.1
1000BASE-T
In 1000BASE-T mode, the transmit data bytes are scrambled to 9-bit symbols and
encoded into 4D PAM 5 symbols. Upon initialization, the initial scrambling seed is
determined by the PHY address. This prevents multiple the I347-AT4 from outputting
the same sequence during idle, which helps to reduce EMI.
3.2.2.2
100BASE-TX
In 100BASE-TX mode, the transmit data stream is 4B/5B encoded, serialized, and
scrambled.
3.2.2.3
10BASE-T
In 10BASE-T mode, the transmit data is serialized and converted to Manchester
encoding.
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