Micrel, Inc.
KSZ8041NL
Collision Detection
The MAC regenerates the COL signal of the MII from TX_EN and CRS_DV.
HP Auto MDI/MDI-X
HP Auto MDI/MDI-X configuration eliminates the confusion of whether to use a straight cable or a crossover cable
between the KSZ8041NL and its link partner. This feature allows the KSZ8041NL to use either type of cable to connect
with a link partner that is in either MDI or MDI-X mode. The auto-sense function detects transmit and receive pairs from
the link partner, and then assigns transmit and receive pairs of the KSZ8041NL accordingly.
HP Auto MDI/MDI-X is enabled by default. It is disabled by writing a one to register 1F bit 13. MDI and MDI-X mode is
selected by register 1F bit 14 if HP Auto MDI/MDI-X is disabled.
An isolation transformer with symmetrical transmit and receive data paths is recommended to support auto MDI/MDI-X.
The IEEE 802.3u Standard defines MDI and MDI-X as follow:
MDI
MDI-X
RJ-45 Pin
Signal
TD+
TD-
RJ-45 Pin
Signal
RD+
RD-
1
2
3
6
1
2
3
6
RD+
RD-
TD+
TD-
Table 4. MDI/MDI-X Pin Definition
Straight Cable
A straight cable connects a MDI device to a MDI-X device, or a MDI-X device to a MDI device. The following diagram
depicts a typical straight cable connection between a NIC card (MDI) and a switch, or hub (MDI-X).
10/100 Ethernet
10/100 Ethernet
Media Dependent Interface
Media Dependent Interface
1
1
Transmit Pair
2
Receive Pair
2
Straight
Cable
3
3
4
4
Receive Pair
5
Transmit Pair
5
6
7
8
6
7
8
Modular Connector
(RJ-45)
Modular Connector
(RJ-45)
HUB
NIC
(Repeater or Switch)
Figure 2. Typical Straight Cable Connection
July 2008
20
M9999-071808-1.2
MICROCHIP [ MICROCHIP ]
