40- and 100-Gbps Ethernet MAC and PHY MegaCore Function User Guide

ID 683114
Date 6/15/2022
Public
Document Table of Contents

3.4.2.2. MDIO Registers

The management data input/output (MDIO) interface is a serial bus interface for the Ethernet. In the 40-100GbE IP core example design, client logic drives the MDIO module when an MDIO serial interface controls the external PMD or CFP device. This serial interface includes two wires, an MDC clock driven by the MAC and a bidirectional data line which can be driven by up to 31 PHY slave devices. The minimum clock frequency is 2.5 MHz. Refer to the specification of your PMD or CFP device for additional information.

Table 68.  MDIO Registers Describes the MDIO registers in the 40-100GbE IP core example design. These registers are typically used to communicate with an external optical module such as a PMD 100G optical module.

Address

Name

Bits

Description

HW Reset Value

Access

0x410

MDIO_WDATA

[15:0]

Data to be written.

0x0000

RW

0x411

MDIO_RDATA

[31]

Link is busy.

1b’0

R

[15:0]

Result of previous read.

0x0000

R

0x412

MDIO_ADDR

[14:10]

PHY address driven to external module.

5’h00

RW

[9:5]

PHY address to access.

5’h00

RW

[4:0]

DEV address.

5’h01

RW

0x413

MDIO_CMD

[3]

Address of the register to be written.

1b’0

RW

[2]

Write signal.

1b’0

RW

[1]

Address of the register to read. This address post increments.

1b’0

RW

[0]

Read signal.

1b’0

RW