CCSTUDIO: Intermixing C and assembly code

Hi Gail,

Apologies for my delayed response. A couple things:

• POP @AH and {POP @AL are not valid C28x instructions. The @ prefix denotes indirect addressing and is not valid as a POP destination. I'm also assuming the stray { in the second POP is a typo. You actually don't need two separate POPs at all. The C28x instruction set provides a single POP ACC instruction that pops a full 32-bit value from the stack directly into the accumulator in one operation. Because your invalid POP instructions never actually load anything from the stack, the subsequent MOVL stores whatever garbage value was already sitting in ACC.
• Before MOVL @_RetAddr, ACC can write to the correct memory location, the Data Page pointer (DP) must be explicitly set to point to your RetAddr variable. Without this step, the MOVL instruction will not store to the correct address, even if ACC contains the right value.

Can you try changing the code to:

unsigned long RetAddr;
asm("POP ACC");
asm("MOVW DP, #_RetAddr");
asm("MOVL @_RetAddr, ACC");

Best Regards,

Delaney

Thanks, Delaney. That fixed the problem.