I am looking at tilings whose vertices lie in a ring of cyclotomic integers. These tilings are of interest as they can have interesting scaling properties or be substitution tilings. Interesting scalings are given by elements of the real subring, especially the units. I have two related questions:

1) What is the real subring of the ring of cyclotomic integers of order n?

2) What are the generators of the group of units of these real subrings?