Watchdog Timer Dynamic Overflow Time for Flash Memory
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Solution Overview
Problem
In embedded microcontrollers, the fixed overflow time setting for watchdog timers can lead to overflow issues during flash memory writing and erasing routines, causing inappropriate data operations.
Innovation Solution
A watchdog timer with an execution address detection section, a timer count section, and a counter clear control section allows for setting a longer overflow time when the program counter enters a specific area, and switching to a shorter overflow time when it exits, enabling independent timing settings for different program areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the overflow time is set to a constant value (several tens to hundreds of milliseconds) for normal routines, then the watchdog timer can reliably detect runaway in normal operations, but the timer overflows during flash memory writing and erasing routines that require several seconds or longer processing time
Solution Approach 1:
The watchdog timer's overflow time is made dynamic rather than fixed. The system automatically switches between a first overflow time (several tens to hundreds of milliseconds) for normal routines and a second overflow time (several seconds or longer) for flash memory operations. This dynamic adjustment allows the timer to adapt to different operational requirements, maintaining reliable runaway detection during normal operations while preventing false overflows during extended flash memory routines.
Solution Approach 2:
The system changes the overflow time parameter based on the execution state. When the program counter enters a predetermined area (indicating flash memory operation), the overflow time parameter is switched from the first value to the second value. When exiting the predetermined area, it switches back. This parameter change resolves the contradiction by matching the timer's tolerance to the actual processing requirements of different operational contexts.
2Duration of action of moving object
If the overflow time is extended to accommodate flash memory operations, then the timer can complete flash routines without overflow, but the user-defined overflow time setting is affected and normal runaway detection may be compromised
Solution Approach 1:
The system dynamically adjusts the overflow time based on operational context rather than using a single extended value. During flash memory operations, the second overflow time (several seconds) is applied to prevent false overflows. During normal operations, the first overflow time (several tens to hundreds of milliseconds) is restored to maintain effective runaway detection. This dynamic switching ensures both flash operation completion and reliable monitoring.
Solution Approach 2:
The overflow time parameter is changed based on the program counter's location. When the program counter is in the predetermined area (flash operation), the parameter switches to the longer second overflow time. When outside this area, it reverts to the shorter first overflow time. This conditional parameter change allows the system to optimize for different operational states without compromising overall reliability.
3Adaptability or versatility
If a special routine for flash memory operations is incorporated, then flash writing and erasing can be performed, but the routine cannot be added without changing the user-defined overflow time setting
Solution Approach 1:
The watchdog timer system provides self-service by automatically detecting when flash memory operations are needed (through program counter monitoring) and adjusting its own overflow time parameter accordingly. The user does not need to manually reconfigure the overflow time or create special handling routines. The system autonomously switches between the first and second overflow times based on whether the program counter is in the predetermined area, eliminating the need for user intervention while adding flash operation capability.
Solution Approach 2:
The watchdog timer is designed with multi-functionality to handle both normal routines and flash memory operations within a single unified system. By incorporating the predetermined area detection and automatic overflow time switching, the timer serves dual purposes: maintaining strict timeout monitoring for normal operations and providing extended tolerance for flash operations. This universal design eliminates the need for separate configurations or routines for different operational modes.
Data Source
AI summary
A watchdog timer including a first register that stores a first overflow time, a second register that stores a second overflow time, a detector and a counter that continues to count a clock signal to the first overflow time. When the detector detects an execution of a program for a flash memory, the counter clears a count value and continues to count the clock signal to the second overflow time.