S32K148 SM_101 Implementation question

[nsiegel]

Hello, our customer has a couple of questions pertaining the last implementation hint of SM_101 for S32K148:   "A checksum may be calculated on safety-critical data at the source prior to transfer, then recalculated at the destination after transfer."

Q1:  How does CRC calculation help with the detection of spurious, excessive, or constant activation?  What is the link here?

Some of our safety-critical data is generated by the ADC module. This data is copied to RAM by the eDMA, which is later on retrieved and used by our code. If we would like to add a CRC to the ADC result data, we would need our C code to access the raw ADC data, meaning that the eDMA would not really be relevant anymore. 

Q2:  How can this implementation hint be compatible with the MCAL implementation of the ADC module? 

[antoinedubois · Accepted solution]

Q1, if you are copying a big piece of memory from one memory to the other, if there were any DMA interference and the data are not copying correctly, you will miss some data in the arrival, therefore the CRC will be incorrect.

Q2: yes the CRC is not relevant for ADC transfer, this is more for these concept they may be more useful:

 For ADC you may also have a way to protect against incorrect ADC sampling (redundancy with plausibility check, Out of range...). You can use this as a safety measure to protect the DMA transfer, in case some sample or lost due to excessive or spurious request.