USB Speed Detection Circuit Using Parallel Receivers
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Solution Overview
Problem
Most USB analyzers can only effectively monitor a single USB speed at a time and rely on unreliable auto speed detection methods, which is problematic during speed changes, such as during high-speed negotiation processes.
Innovation Solution
The use of both a high-speed capable receiver and a full-speed receiver in parallel, with intelligent digital logic to detect USB signaling modes by analyzing SYNC sequences and line-states, allowing for reliable automatic speed detection and configuration of the Physical Interface (PHY) to match the detected speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single receiver is configured to monitor one USB speed, then the receiver can effectively monitor that specific speed, but it cannot reliably detect speed changes or monitor multiple speeds
Solution Approach 1:
The receiver is divided into multiple independent receiver instances, each dedicated to monitoring a specific USB speed (low-speed, full-speed, high-speed). Each receiver operates independently and can detect packets at its designated speed, allowing the system to monitor multiple speeds simultaneously without interference between them.
Solution Approach 2:
The patent introduces a new dimension by adding multiple receivers operating in parallel rather than attempting to make a single receiver multi-speed capable. This dimensional expansion from one receiver to multiple receivers enables simultaneous monitoring of different speeds while maintaining detection reliability through specialized hardware for each speed tier.
2Adaptability or versatility
If auto speed detection is implemented using conventional methods, then the analyzer can attempt to detect speed changes, but the detection is unreliable especially during high-speed negotiation
Solution Approach 1:
The detection function is segmented across multiple specialized receivers, each optimized for its specific speed range. This segmentation allows each receiver to accurately detect packets at its designated speed, providing precise speed detection without the uncertainties of conventional single-receiver auto-detection methods.
Solution Approach 2:
The system continuously monitors packet characteristics from multiple receivers and uses this feedback to dynamically determine the current bus speed. By analyzing which receivers detect packets and their signaling characteristics, the system reliably identifies speed changes and negotiations in real-time.
3Productivity
If the analyzer quickly switches between speed modes to capture negotiation traffic, then it can capture high-speed negotiation processes, but it may miss packets or misidentify speeds during transition
Solution Approach 1:
By segmenting the reception function into multiple independent receivers, the system can quickly switch between speed modes without losing packet capture accuracy. Each receiver maintains continuous monitoring at its designated speed, ensuring that packets are captured reliably during transitions as the active receiver switches between speed modes.
Data Source
AI summary
The Universal Serial Bus (“USB”) 2.0 Specification defines three speeds of communication for its bus, and each has its own signaling characteristics. Due to the uniqueness of each speed, PHYs must be placed in a separate mode for each signaling rate. Although USB devices may know its communication speed, a general purpose USB analyzer must be able to analyze all USB communications. Rather than force the user to manually set the operating mode of the analyzer, this invention describes circuits for automatically and reliably determining the monitored USB communication speed.