A computer data bus interface control selectively connects a computer data bus to functional components of a circuit board or isolates the bus from the functional components. The length of the chamber is calculated according to load changes on the piston where the volume of the chamber changes. The methods also involve, for each group, comparing the watermark bit value to the nominal bit value and, if the nominal bit value and the watermark bit value of the watermark information bit do not match, modifying one or more energy values of one or more corresponding sections in the group such that re-application of the bit assignment rule would assign the watermark bit value to the group.