FSYNC Mismatch Tracking for Line Card ToD Counter Alignment
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Solution Overview
Problem
Network communication boxes experience timing errors due to delays and variations in process, voltage, and temperature (PVT) between frame sync (FSYNC) signals supplied to time of day (ToD) counters, exceeding the Continuous Time Error (CTE) budget, limiting design flexibility.
Innovation Solution
A system with a master line card and slave line card that includes time stamp circuits and phase-locked loops to generate and compare FSYNC signals, adjusting the master line card's timing aspects or applying offsets to compensate for mismatches caused by temperature variations and PVT, ensuring synchronized ToD counters across line cards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If FSYNC signals are supplied to ToD counters in each line card, then time synchronization is achieved, but timing errors occur due to delays and PVT variations
Solution Approach 1:
The system uses feedback mechanisms where time stamps from slave line cards are compared with master line card time stamps to generate mismatch differences. This feedback loop allows the master line card to detect and compensate for timing errors caused by delays and PVT variations, continuously adjusting to maintain synchronization while improving timing accuracy.
Solution Approach 2:
The patent applies parameter changes by adjusting the master line card's timing parameters (phase-locked loop settings and time of day counter offsets) based on measured mismatch differences. By dynamically changing these parameters in response to detected timing errors, the system compensates for delays and PVT variations, resolving the contradiction between achieving synchronization and maintaining precision.
2Measurement precision
If CTE budget is reduced, then timing error is minimized, but design flexibility is limited
Solution Approach 1:
The system implements dynamic adjustment of timing parameters through the phase-locked loop and offset compensation mechanisms. Rather than using fixed design parameters, the master line card continuously adapts its timing characteristics based on real-time mismatch measurements from slave line cards. This dynamic approach allows the system to meet reduced CTE budgets while preserving design flexibility, as the timing parameters can be adjusted during operation rather than being constrained by fixed design choices.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces Continuous Time Error (CTE) by aligning ToD counters across line cards, enhancing design flexibility and accuracy in network timing.
Implementation Method 1
A master line card timing apparatus includes a phase-locked loop that generates a master timing card clock signal from which a plurality of master line card frame sync signals are generated
Implementation Method 2
The master line card further includes a master line card time stamp circuit to provide a plurality of master line card time stamps corresponding to the plurality of master line card frame sync signals
Implementation Method 3
Compare logic compares one of the plurality of slave line card time stamps and one of the plurality of master line card time stamps and generates a baseline difference
Implementation Method 4
the phase-locked loop in the master line card is adjusted based on a difference between the second difference and the baseline difference
Implementation Method 5
providing an offset to a time of day counter on the master line card, the offset corresponding to the difference between the second difference and the baseline difference
Data Source
AI summary
A baseline difference is determined between a slave line card time stamp corresponding to a slave line card frame sync signal and a master line card time stamp corresponding to a master line card frame sync signal. The slave line card generates subsequent slave line card time stamps for subsequent slave line card frame sync signals and the master line card generates subsequent master line card time stamps for subsequent master line card frame sync signals. Current differences are determined between subsequent slave line card time stamps and the subsequent master line card time stamps and the current differences are compared to the baseline difference. When a mismatch difference occurs (current difference differs from the baseline difference), the mismatch difference causes a phase-locked loop in the master line card to be adjusted or an offset to be provided to the master line card time of day counter.