Retiming circuitry for retiming a data signal transmitted from a first environment under control of a first clock signal to a second environment under control of a second clock signal, said first and second clock signals having a known repeat relationship, the retiming circuitry comprising a plurality of delay elements for delaying said data signal; a plurality of inputs connected to said delay elements for receiving said data signal at respectfully different delays; selection means for selecting the data signal at one of said inputs based on said known repeat relationship; and an output for outputting said selected data signal.