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 in two ways:
EEE Negotiation Advertisements can be activated using RX_D1 pin bootstrap. When RX_D1 is set to strap mode 2 or mode 3, EEE capabilities will be advertised during the Auto-Negotiation process. EEE Negotiation Advertisements can also be activated using regsiter access through the SMI. The DP83822 offers two different ways of accessing EEE control registers within the PHY register set. IEEE 802.3az defines MMD3 and MMD7 as the locations for EEE control and status registers. The MMD3 and MMD7 registers 0x3000, 0x3001, 0x3016, 0x703C, and 0x703D contain all the required controls and status indications for operating EEE. Additionally, the DP83822 supports an EEE configuration bypass option that enables EEE control registers within Texas Instruments' Vendor Specific DEVAD. This helps simplify configuration by allowing for a single DEVAD to be used. The Energy Efficient Ethernet Configuration Register #2 (EEECFG2, address 0x04D0) contains controls for enabling and selecting the pin allocation for TX_ER, which is part of the MAC transmit LPI command. The Energy Efficient Ethernet Configuration Register #3 (EEECFG3, address 0x04D1) contains controls for EEE configuration bypass.