DLL-Based Data Reception for Source-Synchronous Bus Misalignment
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Solution Overview
Problem
Source synchronous systems face errors due to inaccuracies in clock generation circuits and uneven distribution of strobe signals within receiving devices, leading to misalignment of data and strobe signals, which affects reception conditions.
Innovation Solution
An apparatus and method using a resistor network and a synchronous receiver with a delay-locked loop (DLL) to generate a delayed data bit signal, compensating for misalignment by adjusting the phase alignment of data strobe and data signals on a synchronous bus, allowing for proper reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data signals and strobe are routed over equal propagation paths on the bus, then the receiver can be relatively certain that data is valid when strobe switching is detected, but inaccuracies in clock generation circuits and additional propagation lengths within the receiving device still cause misalignment and skewing of signals
Solution Approach 1:
The patent applies preliminary action by measuring the propagation delay of the strobe signal through the receiving device beforehand, storing this delay value in a lookup table, and then using this pre-measured information to calculate and apply the appropriate delay to data signals. This pre-characterization approach allows the system to compensate for internal propagation variations without requiring real-time complex measurements, thus resolving the contradiction between reliable data validity detection and precise signal alignment.
Solution Approach 2:
The patent introduces an intermediary approach by using the strobe signal itself as a reference to measure and characterize the internal propagation delay of the receiving device. This measured strobe delay serves as an intermediary parameter that mediates between the external bus signaling (where equal path lengths are maintained) and the internal signal distribution (where path length variations occur), enabling accurate delay compensation for data signals.
2Adaptability or versatility
If the strobe signal is distributed to all internal synchronous receivers within the receiving device, then all receivers can access the strobe, but the additional propagation lengths required route the strobe later than the data signals, skewing the phase of synchronous transmission
Solution Approach 1:
The patent measures the strobe propagation delay through the receiving device in advance and stores this characterization data. This pre-measured delay information is then used to calculate the appropriate delay amount for data signals sent to each receiver, allowing the system to compensate for the inherent propagation length differences caused by distributing the strobe to multiple receivers.
Solution Approach 2:
The patent changes the delay parameter of data signals dynamically based on the measured strobe propagation characteristics. By adjusting the delay amount according to the pre-measured strobe delay and the specific receiver being targeted, the system maintains phase alignment between strobe and data signals despite the varying propagation paths required to reach different internal receivers.
3Productivity
If clock generation circuits are used to gate data signals and switch strobes, then data transmission can be controlled, but inaccuracies due to design margins, fabrication tolerances, or environmental factors cause misalignment of data and strobe signals
Solution Approach 1:
The patent implements feedback by measuring the actual propagation delay of the strobe signal through the receiving device and using this measured information to adjust the timing of data signal transmission. This closed-loop approach compensates for inaccuracies introduced by clock generation circuits, fabrication tolerances, and environmental factors, maintaining precise synchronization between data and strobe signals despite variations in clock circuit performance.
Solution Approach 2:
The patent changes the delay parameter of data signals based on the measured strobe propagation characteristics and the desired reception timing. By dynamically adjusting this delay parameter according to actual device behavior rather than relying solely on theoretical clock timing, the system compensates for clock generation inaccuracies and maintains precise signal synchronization.
Data Source
AI summary
An apparatus that compensates for misalignment on a synchronous data bus. The apparatus includes a resistor network and a synchronous receiver disposed within a receiving device. The resistor network is configured to provide a ratio signal that indicates an amount to delay a data bit signal associated with a data group, where the data bit signal is transmitted by a transmitting device along with a data strobe signal. The synchronous receiver receives the data bit and the data strobe signals, and includes a delay-locked loop (DLL). The DLL is coupled to the ratio signal, and is configured generate a delayed data bit signal, where the DLL adds the amount of delay to the data bit signal to generate the delayed data bit signal, and where the delayed bit signal is delayed relative to the data strobe signal by the amount, thus allowing for proper reception of the data bit signal.