
For more information about the MDIO registers, refer to MAC Configuration Register Space on page 6-1.
MDIO Connection
Figure 4-9: MDIO Interface
PHY
Addr
MDIO Frame
Generation and
Decoding
MDIO Interface
mdc
mdio_in
mdio_out
mdio_oen
PHY
Addr
PHY
Management
Registers
MDIO Frame
Generation &
Decoding
mdio
mdc
addr
PHY
Management
Registers
MDIO Frame
Generation &
Decoding
mdio
mdc
addr
Avalon-MM Control
Interface
10/100/1000 Ethernet MAC
MDIO Frame Format
The MDIO master communicates with the slave PHY device using MDIO frames. A complete frame is 64
bits long and consists of 32-bit preamble, 14-bit command, 2-bit bus direction change, and 16-bit data. Each
bit is transferred on the rising edge of the MDIO clock, mdc.
Table 4-9: MDIO Frame Formats (Read/Write)
Field settings for MDIO transactions.
Command
PREType
IdleData
MSB LSB
TAAddr2
MSB LSB
Addr1
MSB LSB
OP
MSB LSB
ST
MSB LSB
ZxxxxxxxxxxxxxxxxZ0xxxxxxxxxx10011 ... 1Read
Zxxxxxxxxxxxxxxxx10xxxxxxxxxx01011 ... 1Write
Table 4-10: MDIO Frame Field Descriptions
DescriptionName
Preamble. 32 bits of logical 1 sent prior to every transaction.PRE
Start indication. Standard MDIO (Clause 22): 0b01.ST
Opcode. Defines the transaction type.OP
Altera Corporation
Functional Description
Send Feedback
4-21
MDIO Connection
UG-01008
2014.06.30
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