138 Control units of the driveUse shielded twisted-pair cable (~100 ohm, for example, PROFIBUS-compatible cable) forthe wiring. For best immunity, high quality cable is recommended. Keep the cable as shortas possible; the maximum length of the link is 50 meters (164 ft). Avoid unnecessary loopsand running the cable near power cables (such as motor cables). Ground the cable shieldsas described in section Connecting the control cables (page 99).The following diagram shows the wiring of the drive-to-drive link. Safe torque off (XSTO, XSTO OUT)On the inverter control unit [A41], the XSTO input can be used to implement a safe torqueoff (STO) function. For the drive to start, both connections (OUT1 to IN1 and IN2) must beclosed. By default, the terminal block has jumpers to close the circuit. Remove the jumpersbefore connecting an external Safe torque off circuit to the drive. For information on theimplementation of a Safe torque off function, see chapter The Safe torque off function(page 237).Note: The XSTO input only acts as a true Safe torque off input on the inverter control unit[A41]. De-energizing the IN1 and/or IN2 terminals on the supply control unit [A51] will stopthe supply unit but not constitute a true safety function.The XSTO OUT connector is wired to the STO IN connector of one inverter module. Incase the inverter unit consists of multiple modules, the STO OUT connector of one moduleis wired to the STO IN connector of the next module etc. so that all modules are part of thechain. FSO-xx safety functions module connection (X12)See section Implementing the functions provided by the FSO-xx safety functions module(option +Q972 or +Q973) (page 90), and the user manual of the FSO-xx module. SDHC memory card slotThe BCU-x2 has an on-board data logger that collects real-time data from the powermodules to help fault tracing and analysis. The data is stored onto the SDHC memory cardinserted into the SD CARD slot and can be analyzed by ABB service personnel.1234BABGNDShieldXD2DTermination OFF1234BABGNDShieldXD2D1234BABGNDShieldXD2DTermination ONTermination ON
