There are three types of memory access that are affected by security: instruction fetches, JTAG access, and data reads or writes. Instruction fetches are always allowed regardless of the security status of that region. When a memory region is unsecure, all access is allowed, such as JTAG access and data reads or writes from the CPU. When a memory region is secured by one of the two zones, data reads are only allowed by code located in a memory region that is secured by the same zone.