Lots of folks don't "prefer" MMIO.

Now, as is probably no secret, I'm not among their number, but Jan, Erik, and many others have frequently voiced their opposition to MMIO, and their reasons for it. Those reasons are often quite valid.

It's safer to say that MMIO is the "classic" way of attaching external peripherals.

With IIC, SPI, various serial bit-banged schemes, and no shortage of other methods available, MMIO is certainly not the only, and not the preferred, method for interfacing with external hardware, particularly in non-time-critical situations.

The O/P's inquiry, Has really not gotten much attention, however. Is it any wonder the O/P hasn't reappeared? All he wanted was a pointer to a detailed explanation of the external memory bus and its timing, etc.

RE