Whether you're a hobbyist, experimenter, or just curious about electronics, technology, and personal computing, Understanding Data Communications, Fifth Edition, is the perfect guide for you.Written in an easy-to-follow format, this book gives a thorough look at the world of data communications and its impact on our lives. It explores the inner workings of data terminals, transmission channels, fiber optics, and satellites, as well as asynchronous and synchronous modems and interfaces. And, you'll learn how database services, information utilities, and electronic bulletin boards operate.
This book is seriously old but there is some good serial communication specifications. I keep it on my shelf because you never know when you have to understand why your RS-232 is not working.