Mesochronous Clock Alignment Circuit for Low-Latency Data Transfer
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Solution Overview
Problem
Existing technologies face challenges in achieving accurate phase alignment between clock domains with different frequencies, leading to latency and duty cycle distortion in data transfer, particularly in high-speed communication protocols like PCIe and CCIX.
Innovation Solution
The implementation of a phase alignment circuit that includes multiple clock alignment detection circuits and a controller to select the primary alignment circuit, using phase interpolators and local beacon signals to dynamically adjust clock phases, enabling efficient phase alignment in 1:2, 1:1, and 2:1 data transfers without the need for local beacon signals in some cases, and maintaining alignment across varying temperatures and voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase alignment circuits are added to achieve accurate phase alignment between clock domains, then data transfer accuracy is improved, but circuit complexity increases
Solution Approach 1:
The phase alignment functionality is segmented into multiple independent clock alignment detection circuits, each capable of detecting phase alignment points independently. These segmented circuits can operate in parallel and their results are combined by a control circuit, which reduces the complexity of any single detection path while maintaining overall accuracy.
Solution Approach 2:
The system performs preliminary phase alignment detection by monitoring beacon signals before actual data transfer. The clock alignment detection circuits continuously monitor for phase alignment points in advance, allowing the system to pre-establish the optimal phase relationship between clock domains before critical data transfer operations begin.
2Speed
If multiple clock alignment detection circuits are used to find phase alignment points, then phase alignment speed is improved, but the number of circuit components increases
Solution Approach 1:
The detection function is divided into multiple parallel clock alignment detection circuits, each processing a portion of the phase alignment detection task. This segmentation enables simultaneous detection across multiple clock edges and domains, significantly increasing the speed at which phase alignment points are identified while distributing the component count across functional units.
Solution Approach 2:
Each clock alignment detection circuit is designed as a universal module that can detect phase alignment points across different clock domains and frequency ratios (1:2, 2:1, 1:1). This multi-functionality allows the same circuit architecture to be reused multiple times with different configurations, increasing detection speed without proportionally increasing overall system complexity.
3Loss of time
If local beacon signals are used to accelerate phase alignment, then alignment time is reduced, but signal complexity and potential sources of error increase
Solution Approach 1:
Local beacon signals are generated and transmitted before actual data transfer operations to establish phase alignment. These preliminary beacon signals allow the clock alignment detection circuits to identify the optimal phase relationship in advance, reducing the time required for subsequent data transfer operations while keeping the signal structure relatively simple and deterministic.
Solution Approach 2:
The local beacon signals serve as intermediary reference signals that mediate the phase alignment process between different clock domains. Instead of directly analyzing complex data signals for alignment, the system uses these simplified intermediary beacon signals as a clean reference, reducing signal complexity while enabling faster alignment detection.
4Adaptability or versatility
If phase interpolators are used to dynamically adjust clock phases, then adaptability to different clock domains is improved, but circuit complexity and power consumption increase
Solution Approach 1:
The phase interpolator dynamically adjusts the phase of clock signals based on feedback from the clock alignment detection circuits. This dynamic adjustment capability allows the system to adapt to different clock domain frequencies and phase relationships in real-time, improving versatility while using a relatively simple feedback control mechanism to manage the complexity of phase adjustments.
Solution Approach 2:
The phase interpolator changes the phase parameter of clock signals continuously to achieve optimal alignment with different clock domains. By varying this single critical parameter (phase) in response to detection circuit feedback, the system achieves high adaptability across different frequency ratios without requiring complex reconfiguration of the entire clock distribution network.
Data Source
AI summary
Electrical circuits and associated methods relate to performing a phase alignment by providing N copies of clock alignment circuits, enabling and selecting different clock alignment circuits to achieve an initial phase alignment. In an illustrative example, a phase alignment circuit may include a first clock alignment circuit configured to find a first phase alignment point and a second clock alignment circuit configured to find a second phase alignment point. A control circuit may be configured to select a primary clock alignment circuit from the first clock alignment circuit and the second clock alignment circuit and generate a digital command signal to control a phase interpolator. In various embodiments, by setting the control circuit, the same phase alignment circuit may be used to perform phase alignments between clock domains with different frequencies.