This dialog allows specification of memory regions to which memory access should be restricted.
Debug Options dialog, Memory Regions page
An individual region entry specifies the memory space, starting address and end address/region size. The region can have restricted read or write access or 8,16,32-bit access. If read and write access must be restricted, define two regions with equal placement, one with blocked read and the other with blocked write access.
This feature can be used to specify the location of FLASH memory, which can fail if write access is attempted to it (attempting to set a software breakpoint).