I am using 9s12xd64 and 'accidentally' set the ram location start from 0x1000 to 0x1FFF. There are 4K ram on board. It worked fine. I figured out later the ram is supposed to be at the unpaged window of 0x3000. I think if the rpage register is 0xFF, then using the paged window at 0x1000 still makes sense. But I checked the rpage register with Zap debugger. It was 0xfd. Anybody could explain this to me, please. Thanks in advance.