EEE slides Agilent - EDN.com

Energy Efficient Ethernet: How does it work?
Example: Traffic flowing between a remote (server) and local (client) PHYs.
Preconditions: Both devices will advertise and handshake the capability to support
EEE (IEEE802.3az-2010) at power up. Once the handshake is completed, the remote
PHY knows it can initiate a Low Power Idle (LPI) signature (figure 1) to the local PHY.
Figure 1: LPI Signature
- Between periods of activity the remote PHY will send sleep and wake signals.
- Periodic refreshes are sent to the client to update adaptive filters and timing circuits
in order to maintain link integrity.
- When data needs to be transmitted the remote PHY sends a wake signal and data
packets are transmitted.
It is during the low-power state where power savings are realized at the local
PHY because it is allowed to switch off part of the receive and transmit circuitry.
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LPI Mode – Quiet Time Measurement
Quiet Time
Refresh
Cycle
Quiet time measurement between
refresh cycles using burst interval
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LPI Mode Refresh Time (Slave) Measurement…
Refresh Time (slave) - Start of Wake to end of Refresh cycle
Wake (slave)
Refresh Time (slave)
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Sleep 1000 Base-T EEE Signal
Active (Data) Sleep (Idle) Quiet
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Sleep Time Waveform (Decomposition)…
LPI Sleep Time Reference signal
Single Ended Function of original signal
Average Rise Time Trend Function
Measurement Trend of Rise Time Function
Measured Sleep Time
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