NXP(Philips) P89v51RD2 has extra 768bytes of internal data memory (XRAM) that is accessed indirectly with MOVX instruction. Address range for XRAM is 0x0000h to 0x02ffh.
The external data memory (XDATA) address range is 0x0000h-0xffffh. The MCU accesses the external memory if
1) address is 0x0300h or larger. 2) AUXR bit 1 (EXTRAM) is set to 1.
If AUXR bit 1 (EXTRAM) is reset to 0 internal data memory (XRAM) is accessed.
Thus the lower 300h bytes of data memory addresses overlap and the choice is made by AUXR bit 1(EXTRAM).
I wish to use both types of memory. Is there a way to set up the Keil compiler to set/reset the (EXTRAM) AUXR bit_1 so that correct memory is accessed.
If AUXR bit 1 (EXTRAM) is reset to 0 internal data memory (XRAM) is accessed. for addresses below 300h, above that external RAM is accessed
Erik