Erik,

This looks like a fairly new ( but available) part. I couldn't find any info on the "Extended Data Pointer" other than it's SFR address. There is a site reference to the User's Guide but couldn't easily find it, so i don't know how it works.

Phillips does indicate it is compatible with std '51 code (and will run at 2X instruction rate) so perhaps it's just Integrated Banking saving you an external latch. This approach has so far been typical of all the '51 variants (i. e. DS'390) which implement "extended addressing".

P87C51MB2BA (PLCC 44) has a unit 1 price or $7.15 (us) from AVNET.

Now (this is for Erik) the intel 251 implements extended memory using larger integrated registers while remaining '51 source compatible).

regards,
p