Hi Erik,

if I understand you right, you have already 64kB in use, but now you need 65kB. Thus, why you want to use the additional 1kB internal XRAM without disabling the 1kB external RAM on the same address.

Most derivates can use only DPTR for internal XDATA access. So you can use still P2/R0 to access the same address range external, even, if the internal XRAM stay enabled.
On using C you declare this common adress range as PDATA to access always external RAM and as XDATA for internal access.

I think, its impossible for a compiler to support all different ways to enable and disable internal XRAM on all different derivates.
And on some derivates (e.g. Infineon C505) the internal XRAM can only be enabled. And if enabled once, there is no way to switch back.

Also such working, need to call a function for any single byte read or write to select the appropriate memory, and your code grows and the speed decrease dramatically.


Why not use derivates, which support above 64kB ?



Peter