9.1 ROM Zone Size and ROM Zone Registers

Certain applications require that portions of the EEPROM memory array be permanently protected against malicious attempts at altering program code, data modules, security information, or encryption/decryption algorithms, keys, and routines. To address these applications, the memory array is segmented into four different memory zones of 256 bits each. A ROM Zone mechanism has been incorporated, enabling any combination of individual memory zones to be permanently locked so that they become read‑only (ROM). Once a memory zone has been converted to ROM, it cannot be erased, reprogrammed, or unlocked from the ROM state. Table 9-2 shows the address range of each of the four memory zones.