Data Sheet
Ethernet Controller I210 —Interconnects
128
3.7.8.7.3 Receive 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 (see Figure 3-20).
3.7.8.7.3.1 Hybrid
The hybrid subtracts the transmitted signal from the input signal, enabling the use of simple 100BASE-
TX compatible magnetics.
3.7.8.7.3.2 Automatic Gain Control (AGC)
AGC normalizes the amplitude of the received signal, adjusting for the attenuation produced by the
cable.
3.7.8.7.3.3 Timing 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.
3.7.8.7.3.4 Analog-to-Digital Converter (ADC)
The ADC function converts the incoming data stream from an analog waveform to digitized samples for
processing by the DSP core.
3.7.8.7.3.5 Digital Signal Processor (DSP)
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)
• Far-end crosstalk (FEXT)
• Propagation delay variations between channels of up to 120 ns
• Extraneous tones that have been coupled into the receive path
The adaptive filter coefficients are initially set during the training phase. They are continuously adjusted
(adaptive equalization) during operation through the decision-feedback loop.
3.7.8.7.3.6 Descrambler
The descrambler identifies each channel by its characteristic signature, removing the signature and re-
routing the channel internally. In this way, the receiver can correct for channel swaps and polarity
reversals. The descrambler uses the same base 33-bit LFSR used by the transmitter on the other side
of the link.
The descrambler automatically loads the seed value from the incoming stream of scrambled idle
symbols. The descrambler requires approximately 15 s to lock, normally accomplished during the
training phase.