LAN9115-MT Standard Microsystems (SMSC), LAN9115-MT Datasheet - Page 44

• Manufacturer Part Number: LAN9115-MT
• Manufacturer: Standard Microsystems (SMSC)

Specifications of LAN9115-MT

• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (min): 2.97V
• Operating Supply Voltage (max): 3.63V
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 100
• Lead Free Status / RoHS Status: Compliant

APPLICATION NOTE: The user is cautioned to not switch the SMI port while an SMI transaction is in progress.
APPLICATION NOTE: For example, if the internal PHY was operating in 10Mbs mode, and the external PHY was
Revision 1.5 (07-11-08)
3.12
3.12.1
3.12.2
There are two mechanisms that are used to switch between the internal PHY and the external MII port.
SMI Switching
The Serial Management Interface (SMI) port can be switched between the internal PHY and external
MII ports based on the settings of the SMI_SEL bit described in
Configuration
signals.
MII Clock Switching
The LAN9115 supports dynamic switching between the integrated internal PHY and the external MII
port which can connect to an external MII compatible Ethernet PHY device.
The remaining MII signals, with the exception of the SMI port, are switched using a simple multiplexor
controlled by the EXT_PHY_SEL bit described in
Register". It is required that the MII clocks be disabled before the other MII signals are switched.
The steps outlined in the flow diagram in Figure 3.12, "MII Switching Procedure", detail the required
procedure for switching the MII port, including the MII clocks. These steps must be followed in order
to guarantee clean switching of the MII ports.
Using the SMI interface, both the internal PHY, and the external PHY must be placed in a stable state.
For each device generating a TX_CLK or RX_CLK, this clock must be stable and glitch-free before the
switch can be made. If either device is not generating 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 must be stable and glitch-free
for the device that will be selected after the switch. The following must be done prior to a switch:
MII Interface - External MII Switching
A LAN driver or other software controlled mechanism is used to control the PHY_CLK_SEL[1:0]
bits described in
free MII clock switching. This mechanism allows the host processor to disable (gate) the RX_CLK
and TX_CLK clocks from both the internal PHY and the external MII port, and switch the clock
sources once they have stopped. After switching the clocks, the LAN9115 transmitter and receiver
can be re-enabled.
A simple multiplexor that, with the exception of the SMI bus and the MII clocks, will switch the
remaining MII signals. This multiplexor is controlled by the EXT_PHY_EN bit described in
5.3.9, "HW_CFG—Hardware Configuration
The LAN9115 Transmitter must be halted.
The halting of the LAN9115 transmitter must be complete
The LAN9115 Receiver must be halted.
The halting of the LAN9115 receiver must be complete.
The PHY_CLK_SEL field must be set to 10b. This action will disable the MII clocks to the LAN9115
internal logic for both the internal PHY, and the external MII interface.
The host must wait a period of time not less than 5 cycles of the slowest operating clock before
executing the next step in this procedure.
operating at 100Mbs mode, the internal PHY’s TX_CLK and RX_CLK period is the longest,
and will determine the required wait-time. In this case the TX_CLK and RX_CLK period for
the internal PHY is 400ns, therefore the host must wait 2us (5*400ns) before proceeding. If
the clocks of the device being deselected by the switch are not running, they are not
considered in this calculation.
Register". The SMI port can be switched independent of the setting of the other MII
Section 5.3.9, "HW_CFG—Hardware Configuration Register"
DATASHEET
44
Highly Efficient Single-Chip 10/100 Non-PCI Ethernet Controller
Register".
Section 5.3.9, "HW_CFG—Hardware Configuration
Section 5.3.9, "HW_CFG—Hardware
that provides glitch-
SMSC LAN9115
Datasheet
Section