SNIP_CLASSIC_NVM_SECTION_7_11_5_Interaction_with_NVRAM_Manager_NvM

7.11.5 Interaction with NVRAM Manager (NvM) Typically, the Dem module uses nonvolatile memory blocks (configurable in size by the NVRAM Manager [5]) to achieve permanent storage of UDS status information, event related data and required internal states (e.g. retrieve status at startup). Each nonvolatile memory block used from the Dem, needs also to be configured (refer to DemNvRamBlockId). The number, the type, and the content of the used nonvolatile memory blocks are not prescribed. These shall be handled implementation specific. The NvM usage can also be deactivated by configuration (refer to multiplicity of DemNvRamBlockId), so that the Dem will work based on RAM only. [SWS_Dem_00339] Upstream requirements: RS_Diag_04107 ⌈The Dem module shall verify the validity (which relates to block states), integrity (which relates to CRC results), and for general NvM-reading errors of its nonvolatile blocks (before using the respective data).⌋ Usually this verification is done in the API Dem_Init by using NvM_GetErrorStatus for these blocks, which are read by the ECU State Manager (refer to API NvM_ReadAll). Note: For the non-volatile data of the Dem module, it is recommended to configure a CRC in the NvM. [SWS_Dem_00578] Upstream requirements: SRS_Mem_08549 ⌈If the NVM module was not able to read some nonvolatile data of the Dem module, the Dem module shall initialize all non-volatile data with their initial values.⌋ Note: To avoid inconsistencies between readable blocks and erroneous blocks, all nonvolatile data are initialized. The initialization is done to allow the fault detection mechanism of the NvM module, to report the respective reading error(s) to the Dem module (refer to Dem_SetEventStatus). These errors denote the defective NVRAM. [SWS_Dem_00340] Upstream requirements: SRS_BSW_00101 ⌈After the API Dem_Init has finished, the Dem shall be fully operational.⌋ [SWS_Dem_01237] Immediate storage of event related data at first occurrence Upstream requirements: RS_Diag_04211 ⌈If a DTC is configured with DemNvStorageStrategy = IMMEDIATE_AT_FIRST_OCCURRENCE, the Dem shall trigger the storage of its event related data to NvM when the configured trigger DemEventMemoryEntryStorageTrigger to store the data occurs the first time.⌋ Note: For DTCs that are stored immediately at first occurrence, it is necessary to ensure data consistency (e.g. with the UDS status byte) during Dem_Init. Note: Following the storage at first occurrence, any further changes in the event related data will be stored during shutdown (refer to [SWS_Dem_00341]) [SWS_Dem_01238] Storage of event related data at shutdown Upstream requirements: RS_Diag_04211 ⌈If a DTC is configured with DemNvStorageStrategy = DURING_SHUTDOWN or DemNvStorageStrategy is not configured, the Dem shall trigger the storage of the event related data to NvM only during shutdown. (refer to [SWS_Dem_00341])⌋ [SWS_Dem_00102] Upstream requirements: SRS_BSW_00336 ⌈The API Dem_Shutdown shall finalize all pending operations in the Dem module to prepare the internal states and data for transfer to the NVRAM. The event memory shall be locked and not modified until the API Dem_Init is recalled.⌋ [SWS_Dem_00341] Upstream requirements: SRS_BSW_00336, RS_Diag_04211 ⌈The Dem shall trigger the storage of its changed nonvolatile data to NVRAM during Dem_Shutdown.⌋ Based on the Dem configuration and implementation, the copying process to NVRAM of those Demrelated NvMblocks to be stored after Dem_Shutdown, is performed by the API NvM_WriteAll called by the ECU State Manager. If the ECU power supply is disconnected before the NvM has finished copying all data to NVRAM, these data will be incomplete/inconsistent or not stored. At next startup, the events of the last operating cycle could not be found anymore. Therefore, the NVRAM Manager configuration provides mechanisms for data consistency, like redundant data blocks. [SWS_Dem_00164] Upstream requirements: RS_Diag_04077 ⌈The Dem module shall use the APIs NvM_WriteBlock and NvM_ReadBlock of the NVRAM Manager, if there is the necessity to store and restore data between Dem_Init and Dem_Shutdown.⌋ Note: The NvM module realizes a retry mechanism for block reading and writing. Therefore, the Dem module does not implement any retry mechanism for its nonvolatile blocks. [SWS_Dem_00579] Upstream requirements: SRS_BSW_00171 ⌈If the NVM module was not able to write (some) nonvolatile data of the Dem module, the Dem module shall ignore the reported negative return values by the NvM.⌋ Note: If writing of nonvolatile Dem data fails, the Dem module is not able to perform any adequate reaction.