Error Correction Code (ECC)

Techopedia explains Error Correction Code (ECC)

Error correction code is applied to data storage via the following steps:

1. When a data byte or word is stored in RAM or peripheral storage, a code-specifying bit sequence is estimated and stored. Each fixed number of bits per word has an additional fixed number of bits to store this code.
2. When the byte or word is called for reading, a code for the retrieved word is calculated according to the original algorithm and then compared to the stored byte’s extra fixed bits.
3. If the codes match, the data is error free and is forwarded for processing.
4. If the codes do not match, the changed bits are caught through a mathematical algorithm and the bits are immediately corrected.

Data is not verified during its storage period, but is tested for errors when it is requested. If required, the error correction phase follows detection. Frequent recurring errors at the same storage address indicate a permanent hardware error. In this case, the system sends the user a message, which is logged to record the error location(s).