KSZ8851-16MLL_15 Datasheet, PDF (19/86 Pages) Micrel Semiconductor – Single-Port Ethernet MAC Controller with 8-Bit or 16-Bit Non-PCI Interface

Micrel, Inc.
KSZ8851-16MLL/MLLI/MLLU
MDI/MDI-X Auto Crossover
To eliminate the need for crossover cables between similar devices, the KSZ8851-16MLL supports HP-Auto MDI/MDI-X
and IEEE 802.3u standard MDI/MDI-X auto crossover. HP-Auto MDI/MDI-X is the default.
The auto-sense function detects remote transmit and receive pairs and correctly assigns the transmit and receive pairs for
the KSZ8851-16MLL device. This feature is extremely useful when end users are unaware of cable types in addition to
saving on an additional uplink configuration connection. The auto-crossover feature can be disabled through the port
control registers. The IEEE 802.3u standard MDI and MDI-X definitions are as below:
Table 2. MDI/MDI-X Pin Definitions
MDI
RJ45 Pins
1
2
3
6
Signals
TD+
TD-
RD+
RD-
RJ45 Pins
1
2
3
6
MDI-X
Signals
RD+
RD-
TD+
TD-
Straight Cable
A straight cable connects an MDI device to an MDI-X device or an MDI-X device to an MDI device. The following diagram
shows a typical straight cable connection between a network interface card (NIC) and a switch, or hub (MDI-X).
March 12, 2015
Figure 3. Typical Straight Cable Connection
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Revision 2.3