3-13Connection procedureThe connection procedure of the RS-232 port and that of the RS-485 port are shown respectively asfollows (taking the S7902E using the PSE2500-A as an example):If the RS-232 port is used, use an 8-core shielded cable. One end of the cable is a crimped RJ-45connector, which is connected to the RS-232 COM port on the rear panel of the S7902E; the other endis attached with a DB-9 female connector and can be connected to the RS-232 port of PSE2500-A. TheCOM cable is similar to the console cable. For details, see Figure 3-14.If the RS-485 port is used, use a straight through cable to connect the COM port with the RS-485 port onthe PSE2500-A.The PoE monitoring port on the PSR1400-D is an RS-485 port. You can select a proper connectionmethod for the RS-485 port according to the type of the PoE monitoring port on the external powermodule.When the S7900E series adopt only the –48 V DC power, but no external PoE power supply, it isunnecessary to connect the COM port.Connecting Category-5 CablesIntroduction to the RJ-45 connector10Base-T/100Base-TX and 1000Base-T ports of the S7900E series use RJ-45 connectors, supportMDI/MDIX auto-sensing, and adopt category-5 cables. The following figure illustrates the appearanceand pinouts of RJ-45 connector.Figure 3-15 RJ-45 connectorTable 3-2 RJ-45 MDI interface pinouts10Base-T/100Base-TX 1000Base-TPinSignal Function Signal Function1 Tx+ Send data BIDA+ Bi-directional data cable A+2 Tx- Send data BIDA- Bi-directional data cable A-3 Rx+ Receive data BIDB+ Bi-directional data cable B+
