196 Appendix D Connectors and pin assignments209418-ATable 54 lists the RJ-45 (8-pin modular) port connector pin assignments.MDI and MDI-X devicesMedia dependent interface (MDI) is the IEEE standard for the interface tounshielded twisted pair (UTP) cable.For two devices to communicate, the transmitter of one device must connect to thereceiver of the other device. The connection is established through a crossoverfunction, which can be a crossover cable or a port that implements the crossoverfunction internally.Ports that implement the crossover function internally are known as MDI-X ports,where X refers to the crossover function.The following sections describe the use of straight-through and crossover cablesfor connecting MDI and MDI-X devices.Table 54 RJ-45 port connector pin assignmentsPin Signal Description1 RX+ Receive Data +2 RX- Receive Data -3 TX+ Transmit Data +4 Not applicable Not applicable5 Not applicable Not applicable6 TX- Transmit Data -7 Not applicable Not applicable8 Not applicable Not applicableNote: For the transmitter of one device to connect to the receiver ofanother device, the total number of crossovers must always be an oddnumber.
