SNLS638A December 2018 – August 2019 DP83825I
EEE is advertised during Auto-Negotiation. Auto-Negotiation is performed at power up, on management command, after link failure, or due to user intervention. EEE is supported if and only if both link partners advertise EEE capabilities. If EEE is not supported, all EEE functions are disabled and the MAC should not assert LPI. To advertise EEE capabilities, the PHY needs to exchange an additional formatted next page and unformatted next page in sequence.
EEE Negotiation can be activated using Register Access. IEEE 802.3az defines MMD3 and MMD7 as the locations for EEE control and status registers. The MMD3 registers 0x1014, 0x1001, 0x1016, and MMD7 registers 0x203C and 0x203D contain all the required controls and status indications for operating EEE. The Energy Efficient Ethernet Configuration Register #3 (EEECFG3, address 0x04D1) contains controls for EEE configuration bypass. By default, EEE capabilities are bypassed. To advertise EEE based on MMD3 and MMD7 registers, EEE capabilities bypass needs to be disabled (0x04D1.0 = 0, 0x04D1.3 = 0) and EEE Advertisement shall be enabled (MMD7 0x203C.1 = 1).