VCD Toggle-Based Compression for Faster Dynamic IR Simulation
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Solution Overview
Problem
Current technologies lack an efficient method for screening and compressing Value Change Dump (VCD) vectors, which are essential for dynamic IR simulation in integrated circuit design, leading to lengthy verification times and increased design cycles due to the large scale of VCD files and the absence of a unified standard for fragment selection.
Innovation Solution
A VCD vector compression method based on circuit toggle behaviors, involving conversion to a three-dimensional current matrix, preliminary and fine screening based on toggle features, and re-outputting a compressed VCD format file, to shorten the simulation excitation vector length without affecting simulation results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire VCD file is used for dynamic IR simulation, then the simulation results are accurate and reflect actual circuit running state, but the simulation time becomes excessively long and verification efficiency decreases
Solution Approach 1:
The VCD file is divided into multiple time segments based on toggle behavior characteristics. The method identifies and segments high-toggle-rate periods from low-toggle-rate periods, allowing selective simulation of only the critical segments that contribute most to dynamic IR analysis, thereby reducing overall simulation time while maintaining accuracy for critical scenarios
Solution Approach 2:
The method extracts and isolates high-toggle-rate segments from the complete VCD file for separate simulation processing. By taking out only the critical portions containing significant toggle activity and simulating them independently, the approach achieves accurate dynamic IR results without the computational overhead of simulating the entire VCD file
2Productivity
If VCD files are compressed by removing segments, then the simulation speed improves and verification time shortens, but the risk of losing critical worst-case dynamic IR information increases
Solution Approach 1:
The method employs a feedback mechanism where toggle rate information is continuously monitored and used to guide segment selection decisions. By using toggle rate as a feedback criterion, the system can identify segments that contain critical switching activity and ensure they are retained for simulation, thus maintaining result accuracy while enabling compression of non-critical segments
Solution Approach 2:
The approach changes the parameter used for segment selection from arbitrary or uniform criteria to toggle-rate-based criteria. By using toggle rate as the key parameter for identifying critical segments, the method ensures that segments containing significant dynamic activity are preserved while allowing compression of segments with minimal activity, balancing speed and accuracy
3Ease of operation
If designers rely on experience to screen VCD fragments, then some subjective judgment can be applied, but there is no unified standard and the process lacks consistency and repeatability
Solution Approach 1:
The method transforms the subjective experience-based screening process into an objective parameter-driven process by using toggle rate as a quantifiable metric. This parameter change enables consistent, repeatable segment selection that does not depend on individual designer experience, while maintaining ease of operation through automated calculation and comparison of toggle rate values
Data Source
AI summary
Disclosed are a VCD vector compression method and device based on circuit toggle behaviors. The method comprises: converting a VCD format file into a current matrix model, wherein three dimensions of the current matrix model are one time dimension and two spatial dimensions; performing preliminary screening based on an overall toggle feature: dividing the current matrix into several time segments in accordance with an equal interval in the time dimension, and performing screening according to the overall toggle feature, and forming a preliminary screened current distribution matrix by the screened time segments; performing fine screening based on region toggle features: performing further screening according to local toggle features, and forming a fine screened current distribution matrix by the screened time segments; and re-outputting the fine screened current distribution matrix as a VCD format file after vector compression.