An instance of this Function Block type provides a model for bidirectional motion along a single axis with sensors at both ends of its motion. The POS output is expressed in units of 0% to 100% full scale, and the VF and VR inputs are expressed in % of full scale per "tick" of the CLK event input. The HOME and END outputs indicate the 0% and 100% full scale positions. The IND output indicates a change in the POS, HOME and/or END outputs.

Motion stops when the FAULT input is TRUE and resumes when it is FALSE , thus permitting the simulation of simple faults.

The direction and velocity of motion are determined by the internal variable SPEED , derived from the FWD , REV and FAULT inputs as shown in the table below.

See the XBAR_MDLL FB type for an example of the use of an instance of this type.