SMSC FlexPWR LAN8720 - Manual (Page 35)

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
SMSC LAN8720/LAN8720i 35 Revision 1.0 (05-28-09)
DATASHEET
Figure 4.10 MDIO Timing and Frame Structure - READ Cycle
Figure 4.11 MDIO Timing and Frame Structure - WRITE Cycle
MDC
MDI0
Read Cycle
...
32 1's 0 1 1 0 A4 A3 A2 A1 A0 R4 R3 R2 R1 R0 D1
...
D15 D14 D0
Preamble
Start of
Frame
OP
Code
PHY Address Register Address
Turn
Around
Data
Data From Phy Data To Phy
MDC
MDIO ...
32 1's 0 1 1 0 A4 A3 A2 A1 A0 R4 R3 R2 R1 R0
Write Cycle
D15 D14 D1 D0
...
Data Preamble
Start of
Frame
OP
Code
PHY Address Register Address
Turn
Around
Data To Phy