Hi, unsigned int t1, t2; ... t2 = ((t1 & 0xFF) + ((t1 >> 8) & 0xFF)) + (((t1 >> 16) & 0xFF) + ((t1 >> 24) & 0xFF)); If there is assembly instruction that can get sum of four bytes of t1? I think it is often used in video processing! By the way, i use DM6446. Thanks!