P87C51MX on-chip EDATA & XDATA addresses

Hi every one,

The Philips 87C51MX user's manual indicated that the on-chip EDATA ranges from 0x100 to 0xffff; which followed the IDATA.

An article found in the Keil support knowledge base (CX51: LOCATING CODE IN PHILIPS MX INTERNAL CODE MEMORY) showed the following:

---------
User Classes:
EDATA (0x7F0000-0x7F04FF), /*on-chip RAM */

HCONST (0x810000-0x84FFFF) /*off-chip Flash for 'const far' */
---------

How does the "0x7f0000" become the starting address of on-chip EDATA? And where would the on-chip XDATA start?

Thanks.
Deyon

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