Ok, anyway considering that you know what data must be stored there, why are you concerning on that ? If you want to load 0xFF and check it by reading 0xFF the data is supposed correct. There is not a 3rd state than 0 and 1 for the bits, so the only way you have to check if there is a 'problem' in a specific address location is to write/read different patterns (e.g 0x55 and 0xAA) just before writing the correct data to see if it accept all possible values at each bit of each byte.