This is an idiotic way the manufacturer like to tell that it has the internal memory every 8052 derivative has.

It means, 256 bytes, of which 4x8 (00-1F)are "shared" with the register banks, 16 bytes are the bit addressable area (20-2F), all the lower area is direct addressable (00-7F) "data", the upper area (80-FF) is indirect addressable ("idata").

Besides, the RD2 has the 1.75kB of "internal-external" memory, i.e. is is on-chip but accessed via movx @dptr ("xdata").

JW