Hi frnds,
while POWER ON the system i am checking External RAM memory.... but i am not checking the external RAM periodically.....whether the periodic test is needed are not???? Please clarify my doubt....
Wrong contents, but not hw damage?
That makes a big difference.
Checking for hw damage requires you to save the current value, and then write test patterns and read back the test patterns.
Checking for wrong contents requires you to use multiple copies of your data or to checksum the data, and then regularly compare the copies or recompute the checksum.
To not just detect incorrect contents, but to be able to repair it, you will need >= 3 copies of the data to allow majority vote. Or you will need to compute and store some form of error-correction code where you may use two-dimensional checksums, Hamming codes or similar.