So, how is the distinction between indirect and otherwise internal (directly addressable) but not "MOVX" read-write memory made?

This can sometimes be confusing, since there are several ways in which this can be described.

It appears we have three types of internal RAM. First there's the internal RAM from 0x00-0x7F, which is directly OR indirectly addressable. Then, there's the indirectly addressable RAM which occupies the range 0x80-0xFF, which range, when directly addressed, targets the SFR's, in addition to which there are those odd spaces that various manufacturers, notably NXP, among others, as well as Maxim/Dallas and SiLabs, have included, which, in some cases is simply addressed as on-chip pseudo-external (MOVX) RAM.

I haven't run into it myself, but I've read, on this forum, that some devices have extended the internal memory bounds beyond 256 bytes, yet don't address it as (MOVX) xRAM.

Can all this be cleared up, so the nomenclature is clear and unambiguous?

What's the "best", or at least generally accepted, way to describe all these various forms of read/write memory unambiguously?

RE