Mdio Transactions - Xilinx LogiCORE 1000BASE-X User Manual

R
.
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
116
MAC (STA)
Host
Bus I/F
MDIO MDIO
MDC
master
Figure 9-1: A Typical MDIO-managed System
Table 9-1.
Table 9-1: Abbreviations and Terms
Abbreviation
PRE
ST
OP
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Chapter 9: Configuration and Status
PHY1 (MMD)
Configuration
Registers 0 to 31
(REGAD)
MDIO slave
PHY2 (MMD)
Configuration
Registers 0 to 31
(REGAD)
MDIO slave
Term
Preamble
Start of frame
Operation code
Ethernet 1000BASE-X PCS/PMA or SGMII v9.1
Physical
Address
(PHYAD)
= 1
Physical
Address
(PHYAD)
= 2
UG194_5_01_011906
UG155 March 24, 2008