Hi All. A subtle but interesting problem cropped up from a Salvo user ... basically, a service wasn't working because the user had placed Salvo's global variables in xdata space AND Cx51 happened to put something that can be pointed to at X:0000. The run-time error-checking code inside Salvo thought that the parameter passed was a NULL pointer, and rejected the operation. So I have two questions: 1) Does Cx51 always re-organize the order of global variables in a file, when placing them in a data section? Salvo's mem.c specifically has, as its first global variable, one that is never pointed to, so it's OK if it's at a 0x0000 address. But Cx51 jumbled the variables (a bunch of arrays, mainly) around, and one of them ended up at X:0000, which caused the problem. 2) What's the easiest way to ensure that nothing is placed at X:0000? I.e. to start the "valid" xdata space at X:0001 or whatever ... Thanks,