An electronic slave device includes a hardware data packing block having a configurable multiplexing unit having inputs connected to system bus, wires for receiving in parallel each bit of a data word, outputs connected to the respective data write pins of a memory for outputting in parallel each bit of a rearranged data word to be recorded, and rearrangeable connections between the inputs and the outputs according to a set configuration; a format register, the value of which can be set by an external master device to at least two different values; and a logic circuit capable of setting the connections of the multiplexing unit according to the value of the format register to obtain a rearranged data word having at least one symbol with a shifted position in comparison with the position of this symbol in the received data word.