WAGO-I/O-SYSTEM 750 Device Description 23750-652 Serial Interface RS-232 / RS-485ManualVersion 1.4.03.3 Display ElementsFigure 5: Display ElementsTable 8: Legend for Figure “Display Elements”LED Designation Status FunctionA FunctionGreen Ready for operation and undisturbed internal buscommunicationRed Not ready for operation or no or disturbed internal buscommunicationB TxD(transmit)OFF No signal transmission TxDGreen Signal transmission TxD present 1)YellowI/O module has received XOFF character, thetransmission is inactive 2)CTS line has fallen, the transmission is inactive 4)C RxD(receive)OFF No signal transmission RxD or input openGreen Signal transmission RxD present 1)RedSignal transmission RxD present 1) , but some charactersreceived are defective. (parity, data frame or overrunerror has occurred) 3)D TransmissionstatusOFF No transmission errorGreen Output buffer is fullYellowInput buffer is full (LED lights up if there are more than2304 characters in the input buffer. LED does not lightup if there are fewer than 2176 characters in the inputbuffer)E ModeGreen RS-485 half-duplex, DMXYellow RS-422 full-duplex, data exchangeRed RS-232F Data flow controlOFF No data flow controlGreen RTS/CTS data flow control active 4)Yellow XON/XOFF data flow control active 2)Red RTS with lead time and follow-on time is active 5)G Data exchangemode 5)OFF Data exchange mode is OFF 5)Yellow Data exchange mode is initializedGreen Data exchange mode is ONYellowflashingData exchange mode is ON, but there is nocommunication (timeout)