Interrupt Control Circuit for Nested Critical Sections
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Solution Overview
Problem
In real-time systems like modern motor vehicle control units, the frequent and nested disabling and enabling of interrupts result in significant overhead, particularly due to the overhead of up to 15% in control software, caused by the nested calling of functions for interrupt management.
Innovation Solution
A device with control inputs, output signal generators, and a counter is used to manage the nesting of critical program sections by incrementing and decrementing a counter to track the degree of nesting, thereby enabling or disabling interrupts efficiently, and storing processor status registers for restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If interrupts are disabled/enabled frequently and nestedly in critical program sections, then program execution can be protected from interruptions, but software overhead increases by up to 15%
Solution Approach 1:
The device automatically manages interrupt disabling/enabling based on counter state without requiring manual function calls. The hardware circuit self-regulates the interrupt status according to the nesting level indicated by the counter, eliminating the need for software functions to handle this routine task.
Solution Approach 2:
The patent replaces the software-based interrupt management mechanism with a hardware circuit that uses a counter and output signal generators. This hardware substitution eliminates the need for nested function calls in software, directly reducing the 15% overhead while maintaining reliable program protection.
2Reliability
If nested function calls are used for disabling and enabling interrupts, then critical program sections can be properly protected, but control software complexity increases
Solution Approach 1:
The patent extracts the interrupt management functionality from the control software and implements it as a dedicated hardware device. This separation removes the complex nested function calls from the software, reducing control software complexity while maintaining proper critical section protection through the hardware counter and signal generators.
Solution Approach 2:
The hardware device acts as an intermediary between the critical program sections and the interrupt system. The counter and output signal generators provide a simple interface that automatically handles the nesting and dis nesting of interrupt disabled states, eliminating the need for complex software mediation.
Data Source
AI summary
An electronic device comprises one or more control inputs to receive a control signal indicating the beginning of a first critical program section of a program that is running in a system; a counter to be incremented from an initial counter value in response to receipt of the control signal; one or more output signal generators to generate the signal for disabling program interrupts; and an output to output the signal for disabling program interrupts.