The semantic is the same as the restrict keyword in ANSI C99.
It basically means that the structure pointer to by a restricted pointer is not modified by some other alias.
More concretely for the RS08, __restrict is used for the pointer to the parameter block for a channel to allow the compiler to keep parameter values in registers even when calling other functions.
Without restrict, the compiler just knows about a pointer to a struct and would not know that the values in the struct did not change, so he would have to reload them whenever used.
Daniel
