The finite state machine normally controls the board by e.g. the input field signals. Sending a MDI message to the board will force the control value of the digital input pin to the selected state given in the message. With the “Remove mask” function, the control value of the pin is set to the field again. The function is only valid for digital input pins. The message does not influence the (automatic)mode of the board.  

Possible error messages coming from the board
%FAT-UNKCMD-BTSERIAL, Unknown command received
%MDI-UNKCMD-BTSERIAL, No boolean expression
%MDI-UNKCMD-BTSERIAL, Unknown tagname received