Data Sheet

Interconnects—Ethernet Controller I210
129
3.7.8.7.3.7 Viterbi Decoder/Decision Feedback Equalizer (DFE)
The Viterbi decoder generates clean 4DPAM5 symbols from the output of the DSP. The decoder includes
a Trellis encoder identical to the one used by the transmitter. The Viterbi decoder simultaneously looks
at the received data over several baud periods. For each baud period, it predicts whether the symbol
received should be even or odd, and compares that to the actual symbol received. The 4DPAM5 code is
organized in such a way that a single level error on any channel changes an even code to an odd one
and vice versa. In this way, the Viterbi decoder can detect single-level coding errors, effectively
improving the signal-to-noise (SNR) ratio by a factor of 6 dB. When an error occurs, this information is
quickly fed back into the equalizer to prevent future errors.
3.7.8.7.3.8 4DPAM5 Decoder
The 4DPAM5 decoder generates 8-byte data from the output of the Viterbi decoder.
3.7.8.7.3.9 100 Mb/s Operation
The MAC passes data to the PHY over the MII. The PHY encodes and scrambles the data, then transmits
it using MLT-3 for 100TX over copper. The PHY de-scrambles and decodes MLT-3 data received from
the network. When the MAC is not actively transmitting data, the PHY sends out idle symbols on the
line.
3.7.8.7.3.10 10 Mb/s Operation
The PHY operates as a standard 10 Mb/s transceiver. Data transmitted by the MAC as 4-bit nibbles is
serialized, Manchester-encoded, and transmitted on the MDI[0]+/- outputs. Received data is decoded,
de-serialized into 4-bit nibbles and passed to the MAC across the internal MII. The PHY supports all the
standard 10 Mb/s functions.
3.7.8.7.3.11 Link Test
In 10 Mb/s mode, the PHY always transmits link pulses. If link test function is enabled, it monitors the
connection for link pulses. Once it detects two to seven link pulses, data transmission are enabled and
remain enabled as long as the link pulses or data reception continues. If the link pulses stop, the data
transmission is disabled.
If the link test function is disabled, the PHY might transmit packets regardless of detected link pulses.
Setting the Port Configuration register bit (PHYREG 0,16.14) can disable the link test function.
3.7.8.7.3.12 10Base-T Link Failure Criteria and Override
Link failure occurs if link test is enabled and link pulses stop being received. If this condition occurs, the
PHY returns to the auto-negotiation phase, if auto-negotiation is enabled. Setting the Port Configuration
register bit (PHYREG 0,16.14) disables the link integrity test function, then the PHY transmits packets,
regardless of link status.
3.7.8.7.3.13 Jabber
If the MAC begins a transmission that exceeds the jabber timer, the PHY disables the transmit and
loopback functions and asserts collision indication to the MAC. The PHY automatically exits jabber mode
after 250-750 ms. This function can be disabled by setting bit PHYREG 0,16.10 = 1b.