7. An apparatus according to claim 2, wherein the data word format comprises 32 bit data words, the data words in turn comprising either packed bytes or unpacked bytes, wherein a data word having unpacked bytes comprises a single valid byte, a data word with packed bytes contains 32*1-bit, 16*2-bit, 8*4-bit, 4*8-bit, or 2*16-bit data objects, and the normalised output data word comprises 4*8-bit bytes.
7. An apparatus according to claim 2, wherein the data word format comprises 32 bit data words, the data words in turn comprising either packed bytes or unpacked bytes, wherein a data word having unpacked bytes comprises a single valid byte, a data word with packed bytes contains 32*1-bit, 16*2-bit, 8*4-bit, 4*8-bit, or 2*16-bit data objects, and the normalised output data word comprises 4*8-bit bytes. 8. An apparatus according to claim 7, wherein the programming agent indicates to the control unit whether an input data word contains unpacked bytes or packed data objects.