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 programming of parallel slave devices concurrently using an I2C serial bus. At least two slave devices are coupled in parallel on the data transfer bus and configured to load serial data over the serial data line using the communications protocol. Each slave device includes a programmable configuration register configured to be programmed, using the communications protocol, to select one of a plurality of selectable slave device configurations. One of the selectable slave device configurations causes the at least two slave devices to load the serial data in parallel, and another of the selectable slave device configurations causes the at least two slave devices to be loaded one at a time.