KS8721B/BT
Micrel
Auto Crossover (Auto MDI/MDI-X)
Automatic MDI/MDI-X configuration is intended to eliminate the need for crossover cables between similar devices. The
assignment of pin-outs for a 10/100 BASE-T crossover function cable is shown below.
This feature can eliminate the confusion in real applications so both straight cable and crossover cable can be used. This
feature is controlled by register 1f:13. See “Register 1fh–100BaseTX PHY Controller” section for details.
10/100 Base-T
Media Dependent Interface
10/100 Base-T
Media Dependent Interface
1
1
Transmit Pair
Receive Pair
2
2
3
3
4
4
Receive Pair
Transmit Pair
5
5
6
7
8
6
7
8
Modular Connector
(RJ45)
Modular Connector
(RJ45)
HUB
(Repeater or Switch)
NIC
Figure 1. Straight Through Cable
10/100 BASE-T
Media Dependent Interface
10/100 Base-T
Media Dependent Interface
1
1
Receive Pair
Receive Pair
2
2
3
3
4
4
Transmit Pair
Transmit Pair
5
5
6
7
8
6
7
8
Modular Connector (RJ45)
Modular Connector (RJ45)
HUB
(Repeater or Switch)
HUB
(Repeater or Switch)
Figure 2. Crossover Cable
August 2003
15
KS8721B/BT
MICREL [ MICREL SEMICONDUCTOR ]
