R

Chapter 9: Configuration and Status

.

MAC (STA)

PHY1 (MMD)

Host

Bus I/F

MDIO

MDIO

master

MDC

Configuration Registers 0 to 31 (REGAD)

MDIO slave

PHY2 (MMD)

Configuration Registers 0 to 31 (REGAD)

MDIO slave

Physical Address (PHYAD) = 1

Physical Address (PHYAD) = 2

UG194_5_01_011906

Figure 9-1:A Typical MDIO-managed System

The MDIO bus system is a standardized interface for accessing the configuration and status registers of Ethernet PHY devices. In the example illustrated, the Management Host Bus I/F of the Ethernet MAC is able to access the configuration and status registers of two PHY devices via the MDIO bus.

MDIO Transactions

All transactions, read or write, are initiated by the MDIO master. All MDIO slave devices, when addressed, must respond. MDIO transactions take the form of an MDIO frame, containing fields for transaction type, address and data. This MDIO frame is transferred across the MDIO wire synchronously to MDC. The abbreviations are used in this section are explained in Table 9-1.

Table 9-1:Abbreviations and Terms

Abbreviation

Term

 

 

PRE

Preamble

 

 

ST

Start of frame

 

 

OP

Operation code

 

 

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UG155 March 24, 2008

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Xilinx 1000BASE-X manual Mdio Transactions, Configuration and Status, 1Abbreviations and Terms