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LAN9118 Family Programmer Reference Guide
SMSC AN 12.12 23 Revision 1.0 (12-14-09)
APPLICATION NOTE
Figure 5.2 The MII Switching Procedure
1. Both the internal PHY and the external PHY must be placed in a stable state. The TX_CLK and
RX_CLKs of both devices must be stable and glitch-free before the switch can be made. If either
device does not generate a TX_CLK or RX_CLK, this clock must remain off until the switch is
complete. In either case the TX_CLK and RX_CLK of the device that will be selected after the
switch must be stable and glitch-free.
2. The host must command the transmitter to halt, and the halting of the transmitter must be complete
3. The host must command the receiver to halt, and the halting of the receiver must be complete.
TX Stopped?
Halt Transmitter
Halt Receiver
RX Stopped?
Set
PHY_CLK_SEL
to 10b
Clocks Halted?
Set
EXT_PHY_SEL to
Desired MII Port
Set
PHY_CLK_SEL to
Desired MII Port
Enable RX
Enable TX
1
2
3
4
5
6
8
9
11
12
Complete
YES
NO
YES
NO
YES
NO
Using SMI, Set
Internal PHY and
External PHY to a
Stable State
7
13
10
Clocks
Running
YES
NO