is that using the buffers as disclosed in the present invention minimizes the number of memory accesses and therefore reduces power consumption to control access to each circular buffer 200 s 200 r the control circuit 300 comprises a storage unit 310 for storing addresses of current locations within the circular buffers 200 s 200 r for this purpose the storage unit 310 of the control circuit 300 comprises indices vwp 0 320 vwp 1 330 vrp 0 340 and vrp 1 350 the vwp 0 320 is a word index and comprises the address of where in the circular buffer 200 s a next word of sw data is to be loaded the vwp 1 330 is also a word index and comprises the address of where in the circular buffer 200 r a next word of rb data is to be loaded the vrp 0 340 is a byte index and indicates the next byte of data in the circular buffer 200 s to be sent to the accumulation circuit 100 the vrp 1 350 is also a byte index and indicates the next byte of data in the circular buffer 200 r to be sent to the accumulation circuit 100 the present.