One other point about this: If you are trying to map the layout of a hardware register you need to know that the C standard does not constrain how the compiler allocates bit fields. They could be allocated from MSBit to LSBit, from LSBit to MSBit, i= n some other crazy order, with holes between them, etc. ~ Bob Ammerman RAm Systems --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .