... then you'd know that you can expand the I/O and memory resources available to you, and how to do it. If you require that the I/O be on-chip, perhaps you should visit SiLabs' website, as has already been suggested.

NVRAM, such as FRAM, which works just like SRAM aside from the nonvolatility, is full-speed for most, and readily available for use with most 805x's. It doesn't require any specific write-timing loops. It does require a bit more money. The really fast 805x's generally have facilities on-board to allow you to adjust the speed of the external memory bus. There are probably exceptions.

It's possible to construct hardware that preserves the ports that are consumed by external memory bus use. That may not be convenient. YOU have to make the tradeoffs.

RE