I have an embedded board (32 bit address bus, data bus) with 16 MB of memory. The 16 MB consists of Flash, ROM, SRAM and SDRAM. The SDRAM is the higher address memory, and ends at 0x1000000 .
When I view the memoy using the JTAG debugger, all memory above 0x1000000 is shown as '??'. Why is that? How does the JTAG debugger know that I have only 16 MB of RAM? I was under the impression that unused memory addresses are usually mirrored.