Is auto-negotiation of link speed supported in the Gigabit Ethernet MAC Core? In other words, can the Core auto-negotiate between 10 Mbps, 100 Mbps, and 1 Gbps operation?
The Gigabit Ethernet MAC Core does not support link speed auto-negotiation since it only operates at 1 Gbps speeds. However, the Tri-mode Ethernet MAC Core does support this since it can operate at all three speeds: 10/100/1000 Mbps.
For the Gigabit Ethernet only Core, the Status Register (Reg 1) and the Extended Status Register (Reg 15) declare that the GMAC is only able to support 1000BASE-X. Auto-negotiation for 1000BASE-X is a new approach to auto-negotiation performance; this type of auto-negotiation cannot communicate with the older auto-negotiation protocol that is supported by 10/100 speed devices. Consequently, no mechanism exists that can negotiate link speed in the specifications for 1000BASE-X.
The only types of auto-negotiation supported by the GEMAC are the following:
- Auto-negotiation to determine whether a link partner supports Flow Control (this includes determining whether the partner is symmetric or asymmetric).
- Auto-negotiation to determine whether a link partner supports Half or Full Duplex operation.
These types are supported by the 1000BASE-X PCS/PMA version of the Core.