RS-232 Configuration
Port – if * appears next to the port, and it is not the current port, that port is in use by another application.
Baud rate – it is possible to select a baud rate not supported by your UART, typically nothing over 115K except if you have the hardware.
Parity, Data bits and Stop bits – the Modbus default is 8E1, and 8N1 on some newer devices.
RTS control – this allows you to tell the driver the RTS line must be: always on, off or toggle, which is the default setting.
Responsiveness – default = 0. A delay in milliseconds (approximate to within 20) that is instituted before sending a response to any valid or invalid frame.
Load register values at startup – load register values at server startup
Units are all off at startup – this puts all stations as off-line initially, so you have to turn each one on.
Perform MODBUS-MOSCAD checks – this helps testing for a Motorola MOSCAD/Mostrac radio-telemetry unit, then just rejects all requests which would just end up reading "empty" data from one of those units, and returns an exception code to warn the master.