Does anyone know of an Idiot's Guide to this topic? In particular, how does a processor with no special I/O instructions issue a request, e.g. to a serial output device to output "Hello, World"? And how does Memory-Mapped I/O work in detail? Where is the Memory Map stored? What are the actual contents of Device Memory? And where do AMBA/AXI (or ACE) fit in? (I did say it had to be an Idiot's Guide!)
The simpler the example, the better, Alban; if that means normal I/O, fine. Although, UART is in itself an interesting example, having Synchronous versus Asynchronous versions (the latter being akin to what we used to call "Start/Stop Comms". And, unfortunately, I didn't receive your diagram.