Intel Intel Gigabit Ethernet Controllers Spectral Shaper, Low-Pass Filter, Line Driver, PAM-5

PHY Functionality and Features

11.11.3.4Spectral Shaper

This function causes the 4DPAM5 waveform to have a spectral signature that is very close to that of the MLT3 waveform used by 100BASE-TX. This enables 1000BASE-T to take advantage of infrastructure (cables, magnetics) designed for 100BASE-TX.

The shaper works by transmitting 75% of a 4DPAM5 code in the current baud period, and adding the remaining 25% into the next baud period.

11.11.3.5Low-Pass Filter

To aid with EMI, this filter attenuates signal components more than 180 Mhz. In 1000BASE-T, the fundamental symbol rate is 125 Mhz.

11.11.3.6Line Driver

The line driver drives the 4DPAM5 waveforms onto the four twisted-pair channels (A, B, C, D), adding them onto the waveforms that are simultaneously being received from the link partner.

11.11.3.7Transmit/Receive Flow

D0

D1

D2

D3

D4

D5

D6

D7

Scrambler

8

Trellis

Encoder

9

4D PAM-5

PAM-5

Encoded Output to 4-Pair UPT Line

Scrambler Polynomials:

1 + x13 + x33 (Master PHY Mode)

1 + x20 + x33 (Slave PHY Mode)

Figure 11-4. 1000BASE-T Transmit Flow And Line Coding Scheme

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