Hi, all. I seem to have a problem with C51 (DOS) v5.50 and the Atmel AT89S53. The program is all C (no assembler) and accesses different parts of XDATA memory from both the normal main program and also from an interrupt function. It appears that main's xdata addresses are corrupted. The problem goes away if the pragma is removed. The v5.5 release notes say that the MODA2 pragma is only for the AT89S8252, but as I understand it all the Atmel AT89 cores implement the dual pointers in the same way. The problem also goes away if I don't use strcpy, which may point to a library issue. Has anyone else seen this problem? Would a subtle error in the header file for the processor have any bearing on the problem? Your thoughts would be appreciated. Richard