winIDEA shows question marks in the Memory Window

winIDEA shows question marks "??" in the Memory Window whenever a memory read at a specific memory location fails.

Possible reasons

• No physical memory is present at the specific memory.

• The debug interface memory read command fails for some reason.

• The memory is not accessible after the microcontroller power-on-reset and has to be configured first to become accessible respectively visible to the debugger (e.g., ECC-protected memory, NOR flash external memory connected to dedicated Chip-Select signals, SPI flash, etc.).

• When the debugger reads the erased flash cells, which keep a random value after being erased. Such internal flash behavior can be found on the Renesas RH850 and Infineon Traveo T2G.

• Flash and RAM are ECC-protected. Before you can read from the flash location it must be erased and initialized (set to default value). By doing this the ECC is cleared.

• If the application code configures read access restriction, it would cause the read command to fail.

More resources

• Memory Window - winIDEA Help