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....
I forgot to mention one thing.
Are you looking for corrupt memory contents from sw bugs or from glitches in power supply or radiation? Or are you looking for permanently damaged memory cells/signal lines?
I have to check the memory if any location corrupted or not.....
... is to a large extent a residual from the olden magnetic core days. Today the likelyhood of a RAM failure is extremely small.
I have to check the memory if any location corrupted or not the only way to do that is to have 3 copies of the data. If, however, you mean I have to check the memory if any location bad or not then several algorithms are available. However to make such a test relevant, you need to be able to change Vcc to min and max for the test.
Erik
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.
Why do you feel the need to check your memory?
Without knowing the reason for your request, it is impossible to make appropriate suggestions!