I'd never noticed that before! It's an interesting scheme. They actually have put in 384 bytes of internal RAM, of which 128 are addressed in the usual "8051" way, which is directly addressable and apparently plopped in another 128 bytes in addition to the usual upper half of RAM as in the typical 8052 ... or is it?

Here's what it says:"
DATA — 128 bytes of internal data memory space (00h:7Fh) accessed via direct or indirect addressing, using instruction other than MOVX and MOVC. All or part of the Stack may be in this area.

IDATA — Indirect Data. 256 bytes of internal data memory space (00h:FFh) accessed via indirect addressing using instructions other than MOVX and MOVC. All or part of the Stack may be in this area. This area includes the DATA area and the 128 bytes immediately above it."

What are they saying here? Are there 256 bytes or are there 384 bytes? How do you address it? If the indirectly addressable space includes the directly addressable space, then how can they make the claim that they have 128 DATA ram + 256 bytes IDATA ram? If the two are separate, doesn't that create code incompatibilities with other versions?

I suspect this says that there are 256 bytes of RAM in 000-0FFH and no more, but how does that wash with Jesus' experience?

RE