SECDEDsingleerror

SECDED, or Single Error Correct, Double Error Detect, is a class of error-correcting codes used to protect data against bit errors. It is most commonly associated with memory systems, where it provides automatic correction of single-bit faults and detection of double-bit faults, helping to maintain data integrity without requiring retransmission.

The method is typically implemented by extending a Hamming code with an additional parity bit, often called an overall or global parity bit. The data bits are encoded together with a set of Hamming check bits to produce a code word. On readback, the decoder computes a syndrome from the data and check bits and also checks the overall parity. If the syndrome is zero and the parity is correct, no error is present. If the syndrome indicates a single-bit location and the overall parity signals a mismatch, the bit at that location is corrected. If the overall parity is inconsistent but the syndrome does not point to a single-bit location, a double-bit error is detected. The added parity bit therefore enables detection of double errors while preserving the ability to correct single errors.

Applications of SECDED include error protection for DRAM in server and workstation memory, storage controllers, and other systems where data integrity is important. While SECDED can correct single-bit faults and detect double-bit faults, it cannot correct double-bit errors, and some higher-weight errors may be undetectable or detected only by additional checks. Overall, SECDED provides a practical balance between protection and overhead for many commercial and mission-critical environments.