An agricultural machine and method for controlling operation of a user control terminal of the machine are disclosed. The terminal receives user input through a control knob which operates in and is changeable upon a change request user input between first and second knob modes of operation. In the first knob mode, receipt through the control knob of a first function control user input causes a control unit to generate first function control signals and a functional element of an implement of the machine to operate according to the first function control signals, and receipt through the control knob of a second function control user input causes the control unit to generate second function control signals and the functional element to change operation according to the second function control signals. In the second knob mode, the terminal is prevented from receiving function control user input through the control knob.
