Constraint Random Command Sequence Generation for DRAM Testing
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Solution Overview
Problem
As semiconductor technology advances, directional stimulation testing becomes inadequate for large-scale DRAM designs, failing to comprehensively check functions and detect bugs in interactions between specific functions, leading to inefficiencies and missed defects.
Innovation Solution
A method is introduced that generates a random command sequence using a state machine module, where command weights are used to constrain the generation of random commands, ensuring higher randomness and coverage, and addresses are weighted to prioritize unaccessed locations, thereby improving functional testing efficiency and coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If directional stimulation testing is used for small-scale DRAM circuits, then testing can be performed systematically, but it becomes difficult to check all functions completely as design grows larger
Solution Approach 1:
The patent changes the fundamental parameter of test sequence generation from deterministic (directional stimulation) to probabilistic (random generation with constraints). By using a constraint random testing method that generates test sequences based on probability distributions and state machine constraints, the system achieves both systematic coverage and comprehensive function checking for large-scale DRAM designs
Solution Approach 2:
The patent introduces dynamic adaptability in test sequence generation by using state machine constraints that adapt to the current system state. The test generator dynamically adjusts the random command generation based on state transitions and constraints, allowing the testing approach to evolve from static directional stimulation to dynamic constraint-based random testing
2Ease of operation
If separate stimulation files are written for each function, then certain functions can be tested directionally, but unexpected bugs in function interactions are difficult to find
Solution Approach 1:
The patent creates a universal test generation framework that handles multiple functions simultaneously through constraint random testing. Instead of separate stimulation files for each function, a single test generator produces random sequences that naturally exercise multiple functions and their interactions, making the testing approach universally applicable to all DRAM functions
3Reliability
If command sequence is minimized to single command-single command level, then randomness of command transmission increases, but generation complexity increases
Solution Approach 1:
The patent introduces a state machine constraint system as an intermediary between simple random generation and complex systematic testing. This intermediary layer provides the necessary structure and constraints to manage generation complexity while maintaining the benefits of random single-command sequences for high testing coverage
Data Source
AI summary
The embodiments of the disclosure provide a method and device for generating a command sequence, a method and device for testing, and a storage medium. The method for generating a command sequence includes that: at least one executable CMD is determined based on a state machine module according to a current state; a command weight corresponding to the at least one executable CMD is acquired, and a random command is generated from the at least one executable CMD by taking the command weight as a constraint condition; and a next state is determined based on the state machine module according to the random command, and the next state is taken as the current state to continuously execute the step of determining at least one executable CMD based on the state machine module according to the current state, to generate a random command sequence.