USB Link Transition Sequencing for Symmetric Multi-Lane Sync
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Solution Overview
Problem
The USB4 specification lacks detailed implementation steps for transitioning to a symmetric link, which is necessary for optimal data transfer and link management.
Innovation Solution
A method and USB device implementation that involves transmitting RS-FEC blocks, using a lane adapter state machine (LASM) to manage transmitters, and synchronizing transmitters to transmit specific pattern sequences and RS-FEC blocks efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the USB4 specification provides detailed implementation steps for symmetric link transition, then the ease of operation and implementation reliability improve, but the device complexity and specification length increase
Solution Approach 1:
The link transition process is divided into distinct states (U0, U1, U2, U3) with clearly defined transition conditions and actions for each state. This segmentation allows implementers to follow a structured approach without being overwhelmed by the overall complexity, as each state handles only specific tasks.
Solution Approach 2:
The specification pre-defines the transition states and conditions that must be met before proceeding with symmetric link establishment. By establishing the framework of states and transition criteria in advance, implementers can systematically work through the transition process without needing to devise the entire sequence during implementation.
2Speed
If multiple transmitters are synchronized to transmit data simultaneously, then the data transfer speed increases, but the difficulty of detecting and measuring synchronization status increases
Solution Approach 1:
The receiver monitors incoming data blocks and generates feedback information about synchronization status. This feedback mechanism allows the system to detect and measure synchronization conditions by analyzing the received data patterns, making the detection process systematic rather than relying on complex external measurement equipment.
Solution Approach 2:
The specification introduces intermediate signaling mechanisms and data block structures that serve as mediators between multiple transmitters and the receiver. These intermediaries carry synchronization information in a standardized format, simplifying the detection process by providing clear indicators of transmitter coordination status.
Data Source
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AI summary
A method for link transition in a USB device includes transmitting a plurality of first RS-FEC blocks by a first transmitter (S502), receiving an UNBOND set by a receiver (S504), waking up a second transmitter by a LASM when the receiver receives the UNBOND set (S506), transmitting a training sequence by the second transmitter (S508), transmitting a specific pattern sequence by the second transmitter after finishing transmitting the training sequence (S510), determining whether a current RS-FEC block to be transmitted by the first transmitter is a DESKEW block (S512), stopping transmitting the specific pattern sequence if the current RS-FEC block is determined to be the DESKEW block (S514), and transmitting a plurality of second RS-FEC blocks by the first transmitter and the second transmitter (S516).