The register data at address 98h is called the Factory Byte. Either it is custom programmed at the Maxim factory for a specific customer or it is not. If the Factory Byte = AAh, then register addresses 9Bh to 9Ch represent Maxim factory programmed Manufacturing ID values (i.e., data pattern & secret are custom programmed by Maxim). If the Factory Byte = anything else (0x55 and 0x00 are typical values), then 9Bh to 9Ch do NOT represent a Manufacturing ID value and the device was NOT factory programmed by Maxim.