Clock Signal Calibration for Memory Data Transmission
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Solution Overview
Problem
In data transmission systems, particularly in memory systems, calibrating multiple data bits to a common clock signal to ensure they are sampled near the center of their respective eye patterns is challenging due to inherent delays and noise susceptibility, which affects setup and hold time requirements.
Innovation Solution
A method involving coarse and fine grain calibration procedures is employed, where the clock signal delay is adjusted in predetermined step sizes to determine the passing window for each bit, aligning center points, and determining a new clock delay based on calibration data to optimize sampling near the eye pattern center.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a common clock signal is used to sample multiple data bits in parallel, then data transmission efficiency is improved, but the data bits may be at different points of their respective eye patterns causing sampling errors
Solution Approach 1:
The patent applies local quality by allowing each data bit to have its own delay adjustment independent of others. The calibration process determines individual delay values for each bit path, enabling localized optimization of sampling points while maintaining a common clock signal for all bits, thus resolving the contradiction between parallel transmission efficiency and sampling accuracy.
2Measurement precision
If the clock signal is swept across the eye pattern to calibrate sampling points, then sampling accuracy is improved, but the calibration process becomes complex and time-consuming
Solution Approach 1:
The calibration process is segmented into coarse-grain and fine-grain procedures. The coarse-grain calibration performs a broader sweep to identify approximate eye pattern centers, while the fine-grain calibration performs a more precise sweep within a narrower range. This segmentation reduces overall calibration complexity while maintaining high sampling accuracy.
Solution Approach 2:
The coarse-grain calibration is performed as a preliminary action before the fine-grain calibration. By first identifying the approximate center points of eye patterns through coarse calibration, the subsequent fine-grain calibration can focus on a smaller range, reducing the overall calibration time and complexity while achieving high precision.
3Object-affected harmful factors
If the clock delay is adjusted to center points of eye patterns, then noise susceptibility is reduced, but the calibration measurements become more difficult to detect and measure
Solution Approach 1:
The patent employs feedback mechanisms where the results of calibration measurements are used to adjust the clock delay. The system continuously monitors sampling accuracy and adjusts delays to maintain optimal sampling points at eye pattern centers, providing feedback that reduces noise susceptibility while automating the measurement process to reduce difficulty.
Data Source
AI summary
A method and apparatus for calibration of a clock signal used in data transmission is disclosed. The method includes a calibration having coarse and fine grain procedures. The coarse grain procedure begins from the center of a current eye and performs reads while decrementing the delay provided to the clock signal until at least one bit fails. This is repeated, from the center of the eye, incrementing until again at least one bit fails. The lower and upper last passing points are recorded. A fine grain procedure includes performing reads while decrementing, from the lower last passing point, recording points at which each bit fails until all fail. The fine grain procedure further includes incrementing, from the upper last passing point, recording points at which each bit fails until fail. Thereafter, a clock delay corresponding to the center of the new eye is determined based on the calibration data.