Consistent with one example embodiment, communications systems, using a serial data transfer bus having a serial data line and a clock line used to implement a communications protocol, incorporate programmable loading of a logic value into parallel slave device registers. The communications system includes a slave device having two or more registers, each register having two or more bits, each register configured to load data therein received in accordance with the communications protocol over the data transfer bus in a first configuration, and to load a single logic value into the plurality of bits in a second configuration. A programmable configuration register is configured to be programmed, in accordance with the communications protocol over the data transfer bus, to select two or more of the registers for loading of the single logic value into the two or more of bits of the selected registers in the second configuration.