Data Sheet

Ethernet Controller I210 —Interconnects
118
Either side indicates completion of the training phase to its link partner by changing the encoding of the
idle symbols it transmits. When both sides so indicate, the link is up. Each side continues sending idle
symbols each time it has no data to transmit. The link is maintained as long as valid idle, data, or
carrier extension symbols are received.
3.7.8.1.7.2 100BASE-TX
For 100BASE-TX links, the PHY and its link partner immediately begin transmitting idle symbols. Each
side continues sending idle symbols each time it has no data to transmit. The link is maintained as long
as valid idle symbols or data is received.
In 100 Mb/s mode, the PHY establishes a link each time the scrambler becomes locked and remains
locked for approximately 50 ms. Link remains up unless the descrambler receives less than 12
consecutive idle symbols in any 2 ms period. This provides for a very robust operation, essentially
filtering out any small noise hits that might otherwise disrupt the link.
3.7.8.1.7.3 10BASE-T
For 10BASE-T links, the PHY and its link partner begin exchanging Normal Link Pulses (NLPs). The PHY
transmits an NLP every 16 ms and expects to receive one every 10 to 20 ms. The link is maintained as
long as normal link pulses are received.
In 10 Mb/s mode, the PHY establishes link based on the link state machine found in 802.3, clause 14.
Note: 100 Mb/s idle patterns do not bring up a 10 Mb/s link.
3.7.8.2 SmartSpeed
SmartSpeed is an enhancement to auto-negotiation that enables the PHY to react intelligently to
network conditions that prohibit establishment of a 1000BASE-T link, such as cable problems. Such
problems might allow auto-negotiation to complete, but then inhibit completion of the training phase.
Normally, if a 1000BASE-T link fails, the PHY returns to the auto-negotiation state with the same speed
settings indefinitely. With SmartSpeed enabled by setting the Downshift Enable field (bit 11 - refer to
Section 8.27.3.15), after a configurable number of failed attempts, as configured in the Downshift
counter field (bits 14:12 - refer to Section 8.27.3.15) the PHY automatically downgrades the highest
ability it advertises to the next lower speed: from 1000 to 100 to 10 Mb/s. Once a link is established,
and if it is later broken, the PHY automatically upgrades the capabilities advertised to the original
setting. This enables the PHY to automatically recover once the cable plant is repaired.
3.7.8.2.1 Using SmartSpeed
When SmartSpeed downgrades the PHY advertised capabilities, it sets bit Downshift Status (bit 5 -
refer to Section 8.27.3.16). When link is established, its speed is indicated in the Speed field (bits
15:14 - refer to Section 8.27.3.16). SmartSpeed automatically resets the highest-level auto-
negotiation abilities advertised, if link is established and then lost.
Note: SmartSpeed and Master-Slave (M/S) fault - When SmartSpeed is enabled, the M/S number of
Attempts Before Downshift (ABD) is programmed to be less than 7, resolution is not given
seven attempts to try to resolve M/S status (see IEEE 802.3 clause 40.5.2).
Time To Link (TTL) with Smart Speed - in most cases, any attempt duration is approximately
2.5 seconds, in other cases it could take more than 2.5 seconds depending on configuration
and other factors.