Hello, i have problems debugging a XC167 Step AC with ULINK from Keil. I want to transfer two unsigned long values (the first is 0x12345678, the second is 0x08000) from one function to another. The user stack starts at 0xA100, although the stack-section belongs to NDATA-Class (Linker-file NDATA(02000H-03FFFH)) which is accessed via DPP2. First question: why starts the user stack at 0xA100 and not anywhere between 02000H-03FFFH ? The next thing is, that the unsigned long 0x12345678 value changes to 0xFFFFFFFF at the beginning of the called function??? This value is handled over via user stack, which points at this moment to 0xA0FC (value of R[0]= 0xA0FC, I think R[0] operates as userstack-pointer). But around the memory location 0xA0FC you cannot find the value 0x12345678. Why? The other long value which is handled without the user stack is transmitted correctley. If I debugg the same code with the simulator, the value of both variables is correct!!! Thank's a lot. Toby