Continuous Clock Ratio Measurement for Predictive Synchronization

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Solution Overview

Problem

Existing predictive synchronizers are limited in accommodating dynamic frequency changes in clock domains, leading to miss-predictions and metastability issues when clock frequencies drift or ramp, resulting in high latency and data transfer interruptions.

Innovation Solution

A continuous frequency measurement system that measures the ratio of transmit to receive clock domain frequencies over multiple cycles, providing frequent updates to a phase estimator for uninterrupted synchronization, using multiple measurement circuits and counters to maintain up-to-date frequency data.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If high latency measurement circuits are used to obtain frequency information, then measurement accuracy is improved, but synchronization latency increases and the system cannot adapt to dynamic frequency changes

Engineering Contradiction:

Improvefrequency measurement accuracyVSAvoidsynchronization latency

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent implements continuous frequency measurement by overlapping measurement cycles across multiple domains. Instead of sequential measurements, the system performs frequency measurements in transmit, receive, and synchronizer domains simultaneously with overlapping time windows, ensuring continuous updates without interruption. This eliminates idle measurement periods and maintains constant frequency tracking despite the increased computational complexity of continuous operation.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The system performs frequency measurements in advance in the transmit domain before data transmission occurs. By obtaining frequency information proactively and maintaining a buffer of pre-measured frequency data, the system prepares synchronization parameters ahead of time, reducing the latency when actual synchronization decisions must be made during data transfer.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If frequency measurement is performed periodically with fixed intervals, then system simplicity is maintained, but the system cannot adapt to dynamic frequency drift or ramping

Engineering Contradiction:

Improvemeasurement system simplicityVSAvoiddynamic frequency adaptation

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent transforms the static, periodic measurement system into a dynamic one by implementing overlapping measurement cycles with variable timing. The measurement intervals are adjusted based on detected frequency change rates, and the system transitions from fixed periodic updates to adaptive continuous measurement when frequency drift or ramping is detected, allowing the system to respond dynamically to changing conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system implements feedback loops where frequency measurement results from previous cycles inform the timing and parameters of subsequent measurements. When frequency drift or ramping is detected through comparison of consecutive measurements, the system adjusts future measurement intervals and triggers re-synchronization actions, creating a closed-loop adaptive measurement system that responds to actual frequency conditions.

Inventive Principle:

Principle #23Feedback

3Use of energy by moving object

If a single frequency measurement is taken and frequencies are assumed to stay within a small range, then measurement resource usage is minimized, but miss-predictions occur when frequency drift or ramping happens

Engineering Contradiction:

Improvemeasurement energy consumptionVSAvoidsynchronization reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Inventive Principle:

Principle #20Continuity of useful action

4Device complexity

If synchronous measurement is used across all domains, then measurement coordination is simplified, but data transfer interruptions occur due to metastability during measurement states

Engineering Contradiction:

Improvemeasurement coordination complexityVSAvoiddata transfer continuity

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent implements periodic but asynchronous measurement cycles in different domains, where each domain performs measurements at its own optimized intervals rather than forcing synchronous coordination. This allows data transfer to continue uninterrupted in domains not currently in measurement mode, while maintaining periodic updates across all domains to track frequency changes without causing metastability-related interruptions.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS9344099B2Continuous frequency measurement for predictive periodic synchronization

Publication Date: 2016.05.17 ADVANCED MICRO DEVICES INC

AI summary

Embodiments are described for a method of continuously measuring the ratio of frequencies between the transmit and receive clock domains of a heterochronous system using an array of digital frequency measurement circuits that provide overlapping frequency and detection interval measurements within single counter periods required for a single frequency measurement circuit to complete a frequency measurement. Embodiments may be used in a predictive synchronizer to provide low latency, continuous frequency measurements for system-on-chip (SOC) devices that employ frequency drift or ramping to reduce power consumption and overheating conditions.