I generally understand the difference of copyright and patent, however, as software programs are copyrighted, I began to doubt that all hardware specifics are patent protected only. I'm particularly interested in ARM architecture used in smartphones, Wikipedia just says IP (intellectual properly) licensing and I was not able to find definite answer by web search. To understand if any parts of hardware principles could be protected by copyright seems important to me as patents give (only) 20 years protection, but copyright AFAIK times longer.
“Principles” are not protectable by copyright, just their expression. A clever hardware concept will not be covered by copyright but a white paper describing it would be. Also, just like software, the VHDL code or schematic diagram defining a hardware design is protected by copyright. It doesn’t protect the circuit, just the particular representation of the circuit.
There is a special class of copyright material covered by mask works in the US that protect the physical layout of integrated circuits.