Theory Of Operation
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The purpose of the diagnostic is to monitor the validity of the Read Only Memory (ROM) flash memory. A Cyclic Redundancy Check (CRC) checksum is calculated for each memory block of the flash memory and compared with the stored reference checksum. There is a different stored reference checksum for each memory block. If the checksum rationality check of the last memory block has finished, the calculation starts all over again beginning with the first memory block.