I have assigned 0x0000 to 0xF7FF space to the external RAM and the rest space i.e. 0xF800 to 0xFFFF to the I/O devices. Please advice me on the following: 1) The xdata defination in the target files should be 0-F7FF or 0-FFFF? 2) In the startup.a51 file, what should be the configuration of the XDATA 3) I donot want the compiler to allocate any variable or stack in 0xF800 to 0xFFFF space. 4)Does the _at_ defination makes sure that the data being defined there is not initialized to 0 by the startup.a51 and the init.51 files. Regards Mohit