PHY Functionality and Features

 

 

D0

 

 

 

 

 

 

 

 

 

 

 

 

 

D1

 

 

Polynomial

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

D2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

D3

 

8 bits

8 bits

DSP

 

 

 

 

 

 

 

 

GMII

 

 

 

Descrambler

 

PAM-5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Receiver

 

 

 

 

 

 

 

 

 

 

 

 

 

D4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Encoded Input

 

 

 

 

 

 

from 4-Pair UTP Line

 

D5

 

 

 

 

 

 

 

D6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

D7

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 11-5. 1000BASE-T Receive Flow

11.11.4Receive Functions

This section describes function blocks that are used when the PHY receives data from the twisted pair interface and passes it back to the MAC.

11.11.4.1Hybrid

The hybrid subtracts the transmitted signal from the input signal, allowing the use of simple 100BASE-TX compatible magnetics.

11.11.4.2Automatic Gain Control

The Automatic Gain Control (AGC) normalizes the amplitude of the received signal, adjusting for the attenuation produced by the cable.

11.11.4.3Timing Recovery

This function re-generates a receive clock from the incoming data stream which is used to sample the data. On the Slave side of the link, this clock is also used to drive the transmitter.

11.11.4.4Analog-to-Digital Converter

The Analog-to-Digital (ADC) function converts the incoming data stream from an analog waveform to digitized samples for processing by the DSP core.

11.11.4.5Digital Signal Processor

The Digital Signal Processor (DSP) provides per-channel adaptive filtering, which eliminates various signal impairments including:

Inter-symbol interference (equalization).

Echo caused by impedance mismatch of the cable.

Near-end crosstalk (NEXT) between adjacent channels (A, B, C, D).

Software Developer’s Manual

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Intel PCI-X, Intel Gigabit Ethernet Controllers manual Receive Functions