Using the mdio interface, Connecting the mdio to an external phy, Figure 7-11 – Xilinx LOGICORE UG144 User Manual

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1-Gigabit Ethernet MAC v8.5 User Guide

UG144 April 24, 2009

Chapter 7: Using the Physical Side Interface

R

-- DISCONTINUED PRODUCT --

Using the MDIO interface

The MDIO interface is accessed through the optional management interface and is
typically connected to the MDIO port of a physical-layer device to access its configuration
and status registers (see

“MDIO Interface,” on page 86

). The MDIO format is defined in

IEEE 802.3, clause 22.

Connecting the MDIO to an Internally Integrated PHY

The MDIO ports of the GEMAC core can be connected to the MDIO ports of an internally
integrated physical-layer device, such as the MDIO port of the Xilinx Ethernet 1000BASE-
X PCS/PMA or SGMII core. See

Chapter 11, “Interfacing to Other Cores”

for more

information.

Connecting the MDIO to an External PHY

The MDIO ports of the GEMAC core can be connected to the MDIO of an external
physical-layer device. In this situation, mdio_in, mdio_out, and mdio_tri must be
connected to a tri-state buffer to create a bidirectional wire, mdio. This tri-state buffer can
be either external to the FPGA, or internally integrated by using an IOB IOBUF component
with an appropriate SelectIO

TM

standard for the external PHY (illustrated in

Figure 7-11

).

Figure 7-11:

Creating an External MDIO Interface

OBUF

IOB LOGIC

OPAD

O

I

O

I

IO

T

IOPAD

IOB LOGIC

IOBUF

1-Gigabit Ethernet MAC Core

mdc

mdio_tri

mdio_out

mdio_in

MDC

MDIO

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