Network Device Clock Synchronization via Master Clock Extraction
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Solution Overview
Problem
Clock synchronization in network devices is complex, especially in devices with multiple dies or ports, leading to noise and jitter, which can result in inaccurate latency measurements and require significant routing efforts.
Innovation Solution
A network device with frequency generation circuitry, phase-locked loops, and receivers that generate and adjust a clock signal to synchronize with a master clock, reducing absolute clock differential through iterative adjustments, and includes a frequency mixer and clock cleanup PLL to minimize jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple recovered clocks are multiplexed throughout the network device to all ports and lanes, then clock synchronization is achieved, but noise and jitter increase leading to inaccurate latency measurements
Solution Approach 1:
The patent extracts only the essential synchronization function by designating a single master clock source and using it to synchronize all ports and lanes, rather than multiplexing multiple recovered clocks throughout the device. This eliminates the noise and jitter associated with multiple clock sources while maintaining synchronization accuracy.
Solution Approach 2:
The patent segments the clock synchronization function into two distinct parts: a single master clock source that provides the reference, and multiple slave PLLs that independently generate local clocks based on the master. This segmentation avoids the harmful effects of multiplexing multiple clocks while maintaining synchronization.
2Reliability
If multiple recovered clocks are multiplexed throughout the network device, then clock synchronization is achieved, but routing efforts become significant
Solution Approach 1:
The patent extracts the clock distribution function from the data path by using a dedicated master clock source that is separately routed to all slave PLLs. This eliminates the need to multiplex recovered clocks through the data routing infrastructure, significantly reducing routing complexity.
3Measurement precision
If the clock signal is adjusted to synchronize with the master clock, then clock differential is reduced, but frequency generation complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the controller monitors the clock differential between the local clock and master clock, and adjusts the frequency generation circuitry accordingly. This feedback loop automatically maintains accurate clock alignment without requiring complex manual configuration or adjustment mechanisms.
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
This solution simplifies clock synchronization, reduces noise and jitter, and ensures accurate clock alignment across multiple dies and ports without the need for multiplexing recovered clocks, enhancing the scalability and accuracy of clock synchronization in network devices.
Implementation Method 1
a phase-locked loop (PLL) configured to generate a local clock based on the clock signal
Implementation Method 2
a frequency mixer configured to combine the control signal from the controller with an output from the oscillator yielding the clock signal as a combined signal
Implementation Method 3
the frequency generation circuitry includes a voltage-controlled oscillator
Data Source
AI summary
A network device including frequency generation circuitry configured to generate a clock signal, a phase-locked loop configured to generate a local clock based on the clock signal, a plurality of receivers configured to receive respective data streams from respective remote clock sources, each receiver of the plurality of receivers being configured to recover a remote clock from a respective data stream, and a controller configured to identify the remote clock recovered by one of the plurality of receivers as a master clock, find a clock differential between the identified remote clock and the local clock, provide a control signal to the frequency generation circuitry responsively to the clock differential, which causes the frequency generation circuit to adjust the clock signal so as to iteratively reduce an absolute value of the clock differential.