am besten geht sowas über ein Komposit:
Code:
typedef union
{
   unsigned char byte[2];
   unsigned short word;
   struct
   {
       unsigned char low;
       unsigned char high;
   };
} data_t;

data_t data;

...
   data.word = 1234;
   data.b[0] = ...;  //low-Teil
   x = data.low;  //low-Teil