Data Sheet

Ethernet Controller I210 —Interconnects
110
3.7.7.1 Conditions to Enter EEE Tx LPI
In the transmit direction when the network interface is internal copper PHY (CTRL_EXT.LINK_MODE =
00b), entry into to EEE LPI mode of operation is triggered when one of the following conditions exist:
1. No transmission is pending, management does not need to transmit, the internal transmit buffer is
empty, and EEER.TX_LPI_EN is set to 1b.
2. If the EEER.TX_LPI_EN and EEER.LPI_FC bits are set to 1b and a XOFF flow control packet is
received from the link partner, the I210 moves the link into the Tx LPI state for the pause duration
even if a transmission is pending.
3. When EEER.Force_TLPI is set (even if EEER.TX_LPI_EN is cleared).
—If EEER.Force_TLPI is set in mid-packet, the I210 completes packet transmission and then
moves Tx to LPI.
— Setting the EEER.Force_TLPI bit to 1b only stops transmission of packets from the host. The
I210 moves the link out of Tx LPI to transmit packets from management even when
EEER.Force_TLPI is set to 1b.
4. When a function enters D3 state and there’s no management Tx traffic, internal transmit buffers
are empty and EEER.TX_LPI_EN is set to 1b.
When one of the previous conditions to enter a Tx LPI state is detected, assert low power idle is
transmitted on the internal xxMII interface and the I210 PHY transmits sleep symbols on the network
interface to communicate to the link partner entry into Tx LPI link state. After sleep symbols
transmission, behavior of the PHY differs according to link speed (100BASE-TX or 1000BASE-T):
1. While in 100BASE-TX mode, the PHY enters low power operation in an asymmetric manner. After
sleep symbol transmissions, the PHY immediately enters a low power quiet state.
2. While in 1000BASE-T mode, the PHY entry into a quiet state is symmetric. Only after the PHY
transmits sleep symbols and receives sleep symbols from the remote PHY does the PHY enter the
quiet state.
After entering a quiet link state, the PHY periodically transitions between quiet link state, where link is
idle, to sending refresh symbols until a request to transition the link back to normal (active) mode is
transmitted on the internal xxMII TX interface (see Figure 3-14).
Note: MAC entry into Tx LPI state is always asymmetric (in both 100BASE-TX and 1000BASE-T PHY
operating modes).
3.7.7.2 Exit of TX LPI to Active Link State
The I210 exits Tx LPI link state and transition link into active link state when none of the conditions
defined in Section 3.7.7.1 exist. To transition into active link state, the I210 transmits:
1. Normal inter-frame encoding on the internal xxMII TX interface for a pre-defined link rate
dependant period time of Tw_sys_tx-min. As a result, PHY transmits wake symbols for a Tw_phy
duration followed by idle symbols.
2. If the Tw_System_tx duration defined in the EEER.Tw_system field is longer than Tw_sys_tx-min,
the I210 continues transmitting the inter-frame encoding on the internal xxMII interface until the
time defined in the EEER.Tw_system field has expired, before transmitting the actual data. During
this period the PHY continues transmitting idle symbols.
Note: When moving out of Tx LPI to transmit a 802.3x flow control frame the I210 waits only the
Tw_sys_tx-min duration before transmitting the flow control frame. It should be noted that
even in this scenario, actual data is transmitted only after the Tw_System_tx time defined in
the EEER.Tw_system field has expired.