1000BASE-X Standard - 16.2 English

IEEE 802.3-2008 clause 37 describes the 1000BASE-X auto-negotiation function that allows a device to advertise the modes of operation that it supports to a device at the remote end of a link segment (the link partner) and to detect corresponding operational modes that the link partner advertises. The previous figure shows the operation of 1000BASE-X auto-negotiation.

The following describes typical operation when auto-negotiation is enabled.

1. Auto-Negotiation starts automatically when any of the following conditions are met.
   • Power-up/reset
   • Upon loss of synchronization
   • The link partner initiates auto-negotiation
   • An auto-negotiation Restart is requested (See Register 0: Control Register and an_restart_config in Configuration and Status Vectors).
2. During auto-negotiation, the contents of the Auto-Negotiation Advertisement register are transferred to the link partner.

   This register is writable through the MDIO, therefore enabling software control of the systems advertised abilities. See Register 4: Auto-Negotiation Advertisement for more information.

   This register is also writable through the dedicated interface signal an_adv_config_vector . If optional MDIO is present, the additional signal an_adv_config_valid quantifies the contents of an_adv_config_vector. See definitions of an_adv_config_vector and an_adv_config_valid in Configuration and Status Vectors for more information.

   Information provided in this register includes:

   • Fault Condition signaling
   • Duplex Mode
   • Flow Control capabilities for the attached Ethernet MAC.
3. The advertised abilities of the Link Partner are simultaneously transferred into the Auto-Negotiation Link Partner Ability Base register.

   This register contains the same information as in the Auto-Negotiation Advertisement register. See Register 5: Auto-Negotiation Link Partner Base for more information. Remote Fault and pause status bits of this register are also provided in status_vector.

4. Under normal conditions, this completes the auto-negotiation information exchange.

   It is now the responsibility of system management (for example, software running on an embedded Arm® or MicroBlaze™ processor) to complete the cycle. The results of the auto-negotiation should be read from Auto-Negotiation Link Partner Ability Base register. OR by reading the remote_fault and pause status bits of status_vector if MDIO is not present. Other networking components, such as an attached Ethernet MAC, should be configured accordingly. See Register 5: Auto-Negotiation Link Partner Base for more information.

   There are two methods that a host processor uses to learn of the completion of an auto-negotiation cycle:

   • Polling the auto-negotiation completion bit 1.5 in the Status register (Register 1).
   • Using the auto-negotiation interrupt port of the core (see Using the Auto-Negotiation Interrupt.