Cristian:
On the VRS700 part the internal RAM banking window is addressed in the Region of 0x40 to 0x7F of the direct memory address space. When you write in C with this scheme you simply set the stack pointer to 0x80 or above. In this way the stack works in the area that is parallel to the SFR address space. Thus it is out of the way for where the internal memory bank switching goes on.

The main problem I see for a C compiler like Keil for example is the process where the Keil linker tries to build the overlay area in the DATA space. The overlay area could extend up to beyond 0x3F. If it does you are
going to have difficulty. The work arounds if this does happen is to carefully control the number of subroutine arguments, limit amount of local variables in subroutines, or
sxplicitly tag local variables in subroutines to be in XDATA.

Michael Karas