Automotive Semiconductors and Functional Safety
An automotive microcontroller's memory uses ECC (SEC-DED), which can correct 1-bit errors and detect 2-bit errors. What generally happens when read data contains a 2-bit error?
- AErrors of up to 2 bits are automatically corrected using the check bits, so no error is reported and processing continues as is
- BThe error can be neither detected nor corrected, so the erroneous data is used and processing continues
- CIt cannot be corrected but can be detected, so an error is reported and actions such as moving the system to a safe state are taken
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Answer: C. It cannot be corrected but can be detected, so an error is reported and actions such as moving the system to a safe state are taken
SEC-DED (Single Error Correction, Double Error Detection) adds, for example, 8 check bits to 64 bits of data, correcting 1-bit errors and reliably detecting 2-bit errors, although it cannot correct them. When a 2-bit error is detected, the microcontroller reports the error, and software does not use the data and performs a reset or a transition to a safe state. Recording 1-bit errors as well, after correcting them, makes it possible to catch signs of trouble before errors accumulate.
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