Creating Memory device for Nios II processor

IIRC the nios cpu itself doesn't do burst transfers (except optionally for cache line transfers) so you don't need to support them.

If you are worried about the performance of the generated code. You'll get the best code by defining a 'global register variable' to point to a 64k block of address space than contains all the IO (and maybe memory) registers.

Using %gp will generate slight worse code - even with the compiler patches I wrote to enable structure accesses relative to %gp (%gp relative arrays are always worse than global register relative arrays).

In the latter case you do need to use the linker script to assign 'static' addresses to your IO locations.