Real-Time Embedded Multithreading Using ThreadX and MIPS- P14:Although the history of embedded systems is relatively short, 1 the advances and successes of this fi eld have been profound. Embedded systems are found in a vast array of applications such as consumer electronics, “ smart ” devices, communication equipment, automobiles, desktop computers, and medical equipment. | Case Study Designing a Multithreaded System 265 change this value without affecting our design. In addition to the actual data for the event the protected memory must store the priority and time of the event s occurrence. This information is essential in the case where the protected memory becomes full and another event is detected or manually triggered. An event can never overwrite a higher-priority event but it can overwrite an event with the same or lower priority. Figure summarizes the event overwrite rules. As stated previously when the G-force sensors detect a crash the system generates an interrupt with event priority 1. Unsafe driving events are logged as event priority 2 Priority Overwrite Rule When Protected Memory is Full 1 Overwrite the oldest event of Priority 4. If no Priority 4 event exists overwrite the oldest event of Priority 3. If no Priority 3 event exists overwrite the oldest event of Priority 2. If no Priority 2 event exists overwrite the oldest event of Priority 1. 2 Overwrite the oldest event of Priority 4. If no Priority 4 event exists overwrite the oldest event of Priority 3. If no Priority 3 event exists overwrite the oldest event of Priority 2. If no Priority 2 event exists do not save the new event. 3 Overwrite the oldest event of Priority 4. If no Priority 4 event exists overwrite the oldest event of Priority 3. If no Priority 3 event exists do not save the new event. 4 Overwrite the oldest event of Priority 4. If no Priority 4 event exists do not save the new event. Figure Event overwrite rules cioHa oaLeHori tii Krxai LerHiaimi Please purchase PDF Split-Merge on . 266 Chapter 14 warnings as event priority 3 and manual events pushing the emergency button as event priority 4. Our objective is to respond to these events which will appear to the system as interrupts as well as to handle initialization and to process routine data. Design of the System Our design will be simplified and will .
