AUTOSAR diagnostic system event memory management

Event memory management is defined as the process of adding, updating, and deleting event memory entries in the DEM module. The DEM module determines whether an event memory entry is new or currently exists in the event memory.

Event retention

Event retention defines the ability of the DEM module to record and process events (DTCs), UDS status information, and event-related data (e.g., freeze frames, extended data).

The DEM specification specifies six types of event storage conditions. For more information, please refer to the DEM specification manual.

Event Displacement

Event replacement means that the least important, existing event memory entry is replaced by the new event memory entry that needs to be stored. During the replacement process, the least important event memory entry is lost. If the new event memory size exceeds all possible events, no replacement will occur. If the event replacement strategy is disabled, that is, DemEventDisplacementStrategy is set to DEM_DISPLACEMENT_NONE, the DEM disables the event replacement function.

If the event displacement strategy is enabled, that is, DemEventDisplacementStrategy is set to DEM_DISPLACEMENT_FULL or DEM_DISPLACEMENT_PRIO_OCC, the DEM displaces events according to the following principles:

● Event Priority (the most important judging principle, the smaller the number, the higher the storage priority, applicable to FULL or PRIO_OCC strategy)

● Event Active or Passive status (Active storage priority is higher than Passive priority and is applicable to FULL policy)

● Event Occurence Time (Replace older stored events in chronological order,Replace older stored events in chronological order)

Aging of Event

The DEM module provides the ability to delete specific events from the event memory if their failure conditions do not meet the failure conditions within a certain period of time (operation cycle). This process is called "Aging" or "Unlearning". After the event is aged, DEM will delete the relevant event snapshot data (freeze frame) and extended data records.

DemAgingCycleCounterThreshold or DemAgingCycleCounterthresholdforfslc defines the completed aging cycle count value, after which the event memory entry is deleted (aged) from the event memory. When the Aging Counter reaches the DemAgingCycleCounterThreshold, the DTC status bit bit3: confirmedDTC is set to 0. Each Event memory entry has at least one Aging Counter.