Here is one to help a mechanical engineering student trying to program a microcontroller. P5 is a bit addressable register. In the header reg517.h is only the definiton of P5 as a sfr. How do I access a bit address of such a port in C? Do I have to define sbit P5_1=F8H? By the way, Is there an easy way to write the assembly instruction CPL in C51 langauge? Thanks a lot