Minimizing Wander in Asynchronous Mapping Systems
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Solution Overview
Problem
Conventional methods for making justification decisions in asynchronous mapping systems introduce unwanted wander in the regenerated egress client clock due to sequential oscillations of the FIFO fill level, which can be cumulative across intermediate nodes.
Innovation Solution
The solution involves minimizing the effect of these oscillations by averaging multiple samples of the fill level over time or taking samples at non-uniformly spaced intervals, rather than fixed intervals, to make more accurate justification decisions and reduce wander generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fixed interval sampling is used for justification decisions, then the system operation is simple, but sequential oscillations of FIFO fill level cause unwanted wander in the regenerated egress client clock
Solution Approach 1:
The patent changes the sampling parameters by using non-uniformly spaced time intervals instead of fixed intervals. This modifies the sampling methodology to avoid the sequential oscillations that occur with regular sampling, thereby reducing unwanted wander in the regenerated clock signal while maintaining system operability.
Solution Approach 2:
The patent applies preliminary filtering or processing to the fill level samples before making justification decisions. By pre-processing the samples (such as averaging multiple samples or applying a filter), the system prepares more accurate data for decision-making, which reduces the impact of oscillations and improves clock stability.
2Reliability
If multiple samples are averaged or non-uniform intervals are used, then wander generation is minimized, but the device complexity increases
Solution Approach 1:
The patent segments the sampling process into multiple discrete samples taken at different non-uniform intervals. By dividing the single complex sampling operation into multiple simpler sample operations, the system achieves better clock stability through diversified sampling points without requiring a completely new complex control architecture.
Solution Approach 2:
The patent introduces an intermediary processing stage that receives multiple fill level samples and produces a single justification decision. This intermediary layer (which may include averaging logic or filter circuits) absorbs the complexity, allowing the rest of the system to remain relatively simple while still achieving the benefit of reduced wander generation.
3Speed
If conventional justification decisions are made at fixed intervals, then the processing speed is high, but measurement precision of fill level is insufficient leading to wander
Solution Approach 1:
The patent makes the sampling intervals dynamic rather than static. By adjusting the time intervals between samples based on system conditions or using predetermined non-uniform patterns, the system captures fill level variations more accurately without significantly reducing the overall processing speed, thereby improving measurement precision while maintaining operational efficiency.
Data Source
AI summary
A client receive circuit receives client data from a network, decodes the client data and stores the client data within the memory. A frame transmit circuit is provided that includes a justification control logic and a framer and a justification control logic is provided that 1) determines each of a plurality of fill levels and 2) determines an average of the plurality of fill levels. The framer has circuitry to generate a wrapper including a justification opportunity having data based upon a difference between the average and a predetermined threshold.