1. A circuit configuration, comprising: a first input for inputting a first set of digital input data; an output for outputting digital output data; a control input for receiving a control signal; and at least a first register unit and a second register unit, wherein: the circuit configuration writes, as a function of the control signal, in the first register unit at least a part of one of the first set of input data and a second set of input data, and the circuit configuration writes into the second register unit at least a part of one of the first set of input data and the second set of input data; wherein the circuit configuration selects the digital output data from outputs of the first register unit and the second register unit, and wherein register unit outputs corresponding to the first set of input data are always selected over register unit outputs corresponding to the second set of input data.