LAN8810I-AKZE Datasheet, PDF (19/100 Pages) Microchip Technology – GMII 10/100/1000 Ethernet Transceiver with HP Auto-MDIX Support

GMII 10/100/1000 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
Chapter 3 Functional Description
This chapter provides functional descriptions of the various device features. These features have been
categorized into the following sections:
 Auto-negotiation
 HP Auto-MDIX
 GMII Interface
 Serial Management Interface (SMI)
 Interrupt Management
 Resets
 Power-Down modes
 Configuration
 Miscellaneous Functions
 Application Diagrams
3.1 Auto-negotiation
The purpose of the auto-negotiation function is to automatically configure the PHY to the optimum link
parameters based on the capabilities of its link partner. Auto-negotiation is a mechanism for
exchanging configuration information between two link-partners and automatically selecting the highest
performance mode of operation supported by both sides. Auto-negotiation is fully defined in clause 28
and clause 40 of the IEEE 802.3 specification.
Once auto-negotiation has completed, information about the resolved link can be passed back to the
controller via the integrated Serial Management Interface (SMI). The results of the negotiation process
are reflected in the Speed Indication field of the PHY Special Control / Status Register as well as the
Auto Negotiation Link Partner Ability Register.
The advertised capabilities of the PHY are stored in Auto Negotiation Advertisement Register. The
defaults advertised by the device are determined as described in Section 3.8.1.2.2, "Configuring the
Mode of Operation (CONFIG[3:2])," on page 31.
The auto-negotiation protocol is a purely physical layer activity and proceeds independently of the MAC
controller. When enabled, auto-negotiation is started by the occurrence of one of the following events:
 Hardware reset
 Software reset
 Power-down reset
 Link status down
 Setting the Restart Auto-Negotiate bit of the Basic Control Register
On detection of one of these events, the device begins auto-negotiation by transmitting bursts of Fast
Link Pulses (FLP). The data transmitted by an FLP burst is known as a “Link Code Word.” This
exchange of information allows link partners to determine the Highest Common Ability (HCD).
Once a capability match has been determined, the link code words are repeated with the acknowledge
bit set. Any difference in the main content of the link code words at this time will cause auto-negotiation
to re-start. Auto-negotiation will also re-start if all of the required FLP bursts are not received.
Writing the 100BASE-TX Full Duplex, 100BASE-TX, 10BASE-T Full Duplex, and 10BASE-T bits of the
Auto Negotiation Advertisement Register allows software control of the advertised capabilities.
SMSC LAN8810/LAN8810i
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DATASHEET
Revision 1.0 (02-06-13)