![](http://datasheet.mmic.net.cn/200000/NQ80220_datasheet_15086669/NQ80220_50.png)
80220/80221
MD400159/E
50
5.7 MII CONTROLLER INTERFACE
5.7.1 General
The MII controller interface allows the 80220/80221 to
connect to any external Ethernet controller without any
glue logic provided that the external Ethernet controller
has a MII interface that complies with IEEE 802.3, as
shown in Figures 11-12.
5.7.2 Clocks
Standard Ethernet controllers with a MII use TX_CLK to
clock data in on TXD[3:0]. TX_CLK is specified in IEEE
802.3 and on the 80220/80221 to be an output. If a
nonstandard controller or other digital device is used to
interface to the 80220/80221, there might be a need to
clock TXD[3:0] into the 80220/80221 on the edges of an
external master clock. The master clock, in this case,
would be an input to the 80220/80221. This can be done
by using OSCIN as the master clock input; since OSCIN
generates TX_CLK inside the 80220/80221, data on
TXD[3:0] can be clocked into the 80220/80221 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.
5.7.3 Output Drive
The digital outputs on the 80220/80221 controller signals
meet the MII driver characteristics specified in IEEE 802.3
and shown in Figure 14 if external 24.9 ohm 1% termina-
tion resistors are added. These termination resistors are
only needed if the outputs have to drive a MII cable or other
transmission line type load, such as in the external PHY
application shown in Figure 13. If the 80220/80221 is used
in embedded applications, such as adapter cards and
switching hubs shown in Figure 11 and 12, then these
terminations resistors are not needed.
5.7.4 MII Disable
The MII outputs can be placed in the high impedance state
and inputs disabled by setting the MII disable bit in the MI
serial port Control register. When this bit is set to the
disable state, the TP outputs are also disabled and trans-
Figure 14. MII Output Driver Characteristics
I - V
I (mA)
V (Volts)
I
1, V1
–20
1.10
I
2, V2
–4
2.4
I
3, V3
4
0.40
I
4, V4
43
3.05
V
3
I
3
I
4
V
4
Iol
Vol
Voh
V
CC
I
2
V
2
I
1
V
1
Ioh
= 40 ohm
Rol
min
= 40 ohm
Rol
min