First, the dog managed to open the door, there are three mechanisms
1. fixed period task real-time monitoring
2. Non-fixed period task execution time monitoring
3. The logic monitors the execution sequence.
Second, the monitored entity and checkpoints
Watchdog Manager supervise the implementation of the software. Logical unit supervision is supervised entity. AUTOSAR, SW-C, CDD, RTE, there is no fixed relationship between the block BSW module architecture, but usually supervised entity may represent a SW-C SW-C or can be run, or CDD A module BSW depending on the choice of developers.
Supervised entities important position is defined as a checkpoint. The code calls the oversight entities and watchdog Manager intertwined.
Each supervised entity has one or more checkpoints. FIG checkpoints and is formed by the transition between the supervisory entity. The graph is called an internal FIG. In addition, the checkpoint from different entities may be supervised by an external transition. Each watchdog mode manager can have several external graphics.
Graph may have one or more initial check points and one or more final checkpoint. The final checkpoint is correct (assuming that belong to the same checkpoint chart). After the final checkpoint, you can report any initial checkpoint.
In Watchdog Manager, the check may be configured to allow a desired point of time and the external and internal graphics.
At runtime, monitor the Program Manager will verify that executes configured. This is called a logical supervision. Watchdog Manager destroyed the checkpoint and therefore the conversion time. A mechanism for regular check point is called "active supervision", for non-periodic checkpoints, known as the "Deadline supervision"
Watchdog Manager does not repair the checkpoint size. Few coarse-grained checkpoints limit of detection capability Watchdog Manager. Watchdog Manager can detect only whether it can run and check the timing constraints. Conversely, if the SW-C having a checkpoint in each block and having a branch at the run, the watchdog manager may also detect a failure of the control flow in SW-C. High granularity checkpoint can result in large and complex configuration monitoring program manager
Three oversight mechanisms to monitor each entity subject to supervision. Supervised entities can enable one, two or three mechanisms. Calculation of state supervised entity (called the local state).
Determining supervision entity, then determines the state of the entire MCU (referred to as global supervision state) in accordance with each state supervision.
三、Watchdog Handling
Watchdog Manager Watchdog to control the interface to communicate with the hardware watchdog.
Compared with the version V1.xy, Watchdog Manager no longer responsible for the hardware watchdog triggered by the watchdog interface and the watchdog driver. Instead, the Watchdog Manager Watchdog triggers the driver through the interface watchdog report. Then, the watchdog driver is responsible under the condition is true at the correct timing trigger a hardware watchdog. Watchdog trigger condition is a counter value set by the manager cycle. When the hardware watchdog triggered every time, the watchdog driver decrements this counter. When the counter reaches zero, the driver stops the watchdog trigger a hardware watchdog. Thus, when the watchdog manager can not perform, it will automatically cause a watchdog reset (the time required for the counter after decrementing watchdog timeout value plus HW).
Watchdog Manager Watchdog Manager itself may incorrectly set a trigger condition occurs and does not lead to a watchdog reset. Therefore, you may need to use in the Watchdog Manager itself supervised entities and checkpoints while avoiding recursion in the Watchdog Manager.