Saturation in an arithmetic unit

An arithmetic unit for adding a plurality of values to define a result, said arithmetic unit comprising means for receiving said plurality of values; means for adding said plurality of values to define a result, said result being within a first range; means for determining if said result fall within a second range, said second range being smaller than the first range, said means being arranged to consider only some of the bits of said result; and means for modifying said result in so that the result output by said arithmetic unit falls within the second range.