Data-Strobe Decoder Timing for Low-Skew SpaceWire Links
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Solution Overview
Problem
SpaceWire systems face challenges in recovering data from signal pairs with tight constraints on transmission line skew and high costs due to the need for expensive lines, and experience jitter from varying transmission lengths and latency, while also being limited by standardized communication specifications that restrict information transmission.
Innovation Solution
A method and decoder for recovering data from a received signal pair by sampling and combining data and strobe signals, allowing for re-timing synchronized with a receiver clock, and adjusting transmission timing to reduce jitter and enable flexible information transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the exclusive-OR technique is used to recover the clock from data-strobe signals, then data can be decoded, but tight constraints on transmission line skew are required which increases cost
Solution Approach 1:
The patent introduces a delay element as an intermediary component between the strobe signal and the data signal. This delay element compensates for transmission line skew by delaying one of the signals to align them in time, eliminating the need for expensive tightly-matched transmission lines while maintaining reliable data decoding through the XOR operation
2Loss of information
If time code is transmitted after completion of current transmission, then timing information is provided, but variation in transmission length causes jitter
Solution Approach 1:
The patent applies preliminary action by pre-calculating and inserting a delay period before the time code transmission begins. This delay is specifically designed to compensate for the variable transmission length, ensuring that the time code always arrives at a predictable time point relative to the request, thereby eliminating jitter while maintaining accurate timing information delivery
3Ease of operation
If standardized communication specification is followed, then communication protocol is established, but information transmission is limited to defined data and control information
Solution Approach 1:
The patent applies dynamics by making the bit width of data periods variable rather than fixed. Different bit widths are used to encode different types of information: standard data characters, control characters, and time codes. This dynamic adaptation allows the system to transmit diverse information types while maintaining compatibility with the standardized SpaceWire communication protocol
Data Source
AI summary
There is disclosed a method and apparatus for recovering data from a received signal, the received signal including a first signal comprising data bits and a second signal having transitions at data bit boundaries of the first signal where there is an absence of transitions, the method comprising: receiving the first signal; receiving the second signal; sampling the first signal to detect an edge transition of the first signal; sampling the second signal to detect an edge transition of the second signal; wherein on an active edge of either said first or said signal, the current value of the first signal is recovered as a received data bit.