Draft 6/5/00
MII Controller Interface
A-15
Copyright 2000 by LSI Logic Corporation. All rights reserved.
A.9 MII Controller Interface
The MII controller interface allows the L80223 to connect to any external
Ethernet controller without any glue logic, provided the external Ethernet
controller has an MII interface that complies with IEEE 802.3, as shown
in
Figure A.1
through
Figure A.3
.
A.9.1 Clocks
Standard Ethernet controllers with an MII use TX_CLK to clock data in
on TXD[3:0]. TX_CLK is specified in IEEE 802.3 and on the L80223 to
be an output. If a non-standard controller or other digital device is used
to interface to the L80223, there might be a need to clock TXD[3:0] into
the L80223 on the edges of an external master clock. The master clock,
in this case, would be an input to the L80223. To do this, use OSCIN as
the master clock input. Because OSCIN generates TX_CLK inside the
L80223, data on TXD[3:0] can be clocked into the L80223 on edges of
output clock TX_CLK or input clock OSCIN. In the case where OSCIN is
used as the input clock, a crystal is no longer needed on OSCIN, and
TX_CLK can be left open or used for some other purpose.
A.9.2 Output Drive
The digital outputs on the L80223 controller signals meet the MII driver
characteristics specified in IEEE 802.3 and shown in
Figure A.6
if
external 24.9
1% termination resistors are added. These termination
resistors are only needed if the outputs must drive an MII cable or other
transmission line type load, such as in the external PHY application
shown in
Figure A.3
. If the L80223 is used in embedded applications,
such as adapter cards and switching hubs (see
Figure A.1
and
Figure A.2
), these termination resistors are not needed.