A foot operable controller for a surgical instrument having a main foot pedal assembly providing either proportional or linear control signals when moved laterally and in a vertical direction. Friction between an operator's foot and the foot pedal is minimized by a foot pad having a rotating heel plate. A neutral zone between left and right control positions of the foot pedal enables the operator to move his foot freely without changing control settings. Vertical displacement of the foot pedal is indicated by a plurality of mechanical detents during both upward and downward travel. Changing detent resistance alerts the operator to the vertical position of the foot pedal, indicating that further vertical displacement will change an instrument control signal corresponding to the new foot pedal position, thus providing sensory feedback to the operator indicating a change in the functional mode when the foot pedal is moved.