This is basic electronics; so you need to search for books, tutorials, courses, etc on Basic Electronics - in particular, digital electronics.

If this is for professional interest, I strongly recommend that you enrol on a proper course;
even for hobbyist interest, you may be able to find some local courses.

If this is hobbyist interest, the hobbyist magazines often have tutorials. They would also be a good source for books, etc.

Is there a local electronics club that you could join?

http://www.8052.com/forum/read/95853

http://www.kpsec.freeuk.com/index.htm


http://www.8052.com/links