Windowed Watchdog Circuit for Fast and Slow Strobe Fault Detection
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Solution Overview
Problem
Conventional watchdog circuits lack the ability to effectively differentiate between fast and slow rates of watchdog strobe signals, which can lead to inadequate detection of software malfunctions and system failures in safety-critical applications.
Innovation Solution
A windowed watchdog circuit system that includes both a slow timer module and a fast timer module to determine gap times between watchdog strobe signals, outputting a reset state when either threshold is exceeded, with a latch and delay module to manage state transitions and a logic block to ensure accurate system resets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-sided watchdog circuit is used, then the device complexity is reduced, but the measurement precision of strobe rate detection deteriorates
Solution Approach 1:
The watchdog circuit is segmented into two independent timer modules: a slow timer module for detecting slow/missing strobes and a fast timer module for detecting fast-rate strobes. Each timer independently monitors the watchdog strobe signal within its specific time window, enabling precise detection of different strobe rate anomalies without requiring a single complex timer system.
2Measurement precision
If a windowed watchdog circuit with dual timer modules is used, then the measurement precision of strobe rate detection is improved, but the device complexity increases
Solution Approach 1:
Each timer module is optimized for its specific detection function with locally adapted parameters: the slow timer uses a longer time window (Tslow) suitable for detecting missing or slow strobes, while the fast timer uses a shorter time window (Tfast) for detecting fast-rate strobes. This local optimization allows each module to operate independently with simplified logic tailored to its specific detection task.
Solution Approach 2:
The detection capability is extended from a single time dimension to multiple time dimensions by introducing two distinct time windows (Tslow and Tfast). This dimensional expansion allows the system to detect strobe rate anomalies across a broader spectrum without requiring a single complex adaptive timer, thereby improving detection precision while maintaining manageable circuit complexity.
3Reliability
If the watchdog circuit uses external hardware implementation, then the reliability is improved, but the ease of manufacture deteriorates
Solution Approach 1:
The watchdog circuit is designed as a universal hardware module that can be integrated into various embedded systems and safety-critical applications. The standardized architecture with clear input/output interfaces and configurable time parameters (Tslow, Tfast) allows the same circuit design to be manufactured and deployed across different platforms, improving ease of manufacture while maintaining high reliability through hardware-based detection.
Data Source
AI summary
A windowed watchdog circuit system can include a slow timer module configured to receive watchdog strobe signals from a processor and to determine whether a gap time between watchdog strobe signals is longer than a slow threshold time to output a slow threshold state when the gap time is longer than the slow threshold. The windowed watchdog circuit system can include a fast timer system configured to receive the watchdog strobe signals from the processor and to determine whether the gap time between watchdog strobe signals is shorter than a fast threshold time to output a fast threshold state when the gap time is shorted than the fast threshold. The windowed watchdog circuit system can be configured to output a reset state to reset the processor when any of the slow timer module and the fast timer system are outputting the slow threshold state or the fast threshold state, respectively.