17: USER COMMUNICATION INSTRUCTIONS« FC4A MICRO SMART USER ’S MANUAL » 17-29RS232C Line Control SignalsWhile the MicroSmart is in the user communication mode, special data registers can be used to enable or disable DSR andDTR control signal options for port 2. Port 2 is available on the 16- and 24-I/O type CPU modules only, and an optionalRS232C adapter must be installed on the port 2 connector to enable the RS232C communication. The DSR and DTR con-trol signal options cannot be used for port 1.The RTS signal line of port 2 remains on.Special Data Registers for Port 2 RS232C Line Control SignalsSpecial data registers D8104 through D8106 are allocated for RS232C line control signals.Control Signal Status D8104Special data register D8104 stores a value to show that DSR and DTR are on or off at port 2. The data of D8104 is updatedat every END processing.DSR Control Signal Status in RUN and STOP ModesDTR Control Signal Status in RUN and STOP ModesRS232C Port DR No. Data Register Function DR Value Updated R/WPort 2D8104 Control signal status Every scan RD8105 DSR input control signal option When sending/receiving data R/WD8106 DTR output control signal option When sending/receiving data R/WD8104 Value DTR DSR Description0 OFF OFF Both DSR and DTR are off1 OFF ON DSR is on2 ON OFF DTR is on3 ON ON Both DSR and DTR are onCommunicationMode D8105 Value DSR (Input) StatusRUN Mode STOP ModeUserCommunicationMode0 (default) No effect No effect (TXD/RXD disabled)1 ON: Enable TXD/RXDOFF: Disable TXD/RXD No effect (TXD/RXD disabled)2 ON: Disable TXD/RXDOFF: Enable TXD/RXD No effect (TXD/RXD disabled)3 ON: Enable TXDOFF: Disable TXD No effect (TXD/RXD disabled)4 ON: Disable TXDOFF: Enable TXD No effect (TXD/RXD disabled)5 or more No effect No effect (TXD/RXD disabled)Maintenance Mode — No effect No effectCommunicationMode D8106 Value DTR (Output) StatusRUN Mode STOP ModeUserCommunicationMode0 (default) ON OFF1 OFF OFF2 RXD enabled: ONRXD disabled: OFF OFF3 or more ON OFFMaintenance Mode — ON ON
