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LAN8810I-AKZE Datasheet, PDF (25/100 Pages) Microchip Technology – GMII 10/100/1000 Ethernet Transceiver with HP Auto-MDIX Support
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3.4
GMII 10/100/1000 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
Serial Management Interface (SMI)
The Serial Management Interface is used to control the device and obtain its status. This interface
supports the standard PHY registers required by Clause 22 of the 802.3 standard, as well as “vendor-
specific” registers allowed by the specification. Non-supported registers (such as 11 to 14) will be read
as hexadecimal “FFFF”. Device registers are detailed in Chapter 4, "Register Descriptions," on
page 43.
At the system level, SMI provides 2 signals: MDIO and MDC. The MDC signal is an aperiodic clock
provided by the station management controller (SMC). MDIO is a bi-directional data SMI input/output
signal that receives serial data (commands) from the controller SMC and sends serial data (status) to
the SMC. The minimum time between edges of the MDC is 160 ns. There is no maximum time
between edges. The minimum cycle time (time between two consecutive rising or two consecutive
falling edges) is 400 ns. These modest timing requirements allow this interface to be easily driven by
the I/O port of a microcontroller.
The data on the MDIO line is latched on the rising edge of the MDC. The frame structure and timing
of the data is shown in Figure 3.1 and Figure 3.2. The timing relationships of the MDIO signals are
further described in Section 5.5.7, "SMI Timing," on page 95.
Read Cycle
MDC
MDIO
32 1's 0 1
Preamble
Start of
Frame
10
OP
Code
A4 A3 A2 A1 A0 R4 R3 R2 R1 R0
D15 D14
PHY Address
Register Address
Turn
Around
...
...
Data
D1 D0
Data To Phy
Data From Phy
Figure 3.1 MDIO Timing and Frame Structure - READ Cycle
Write Cycle
MDC
MDIO 32 1's 0 1
Preamble
Start of
Frame
01
OP
Code
A4 A3 A2 A1 A0 R4 R3 R2 R1 R0
D15 D14
PHY Address
Register Address
Turn
Around
...
...
Data
D1 D0
Data To Phy
Figure 3.2 MDIO Timing and Frame Structure - WRITE Cycle
SMSC LAN8810/LAN8810i
25
DATASHEET
Revision 1.0 (02-06-13)
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