Source Synchronous Bus Signal Alignment Using Replica Distribution
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Solution Overview
Problem
Source synchronous data strobes and data signals are prone to misalignment due to design inaccuracies, fabrication tolerances, and environmental factors, limiting the operating frequency of devices and requiring manual compensation that is inefficient and suboptimal.
Innovation Solution
An apparatus and method that dynamically adjusts the phase alignment of data strobes and data signals using a replica radial distribution element, JTAG interface, and bit lag control element, which measures and compensates for propagation time variations to ensure optimal synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If source synchronous data strobes and data signals are transmitted at high bus speeds, then data transfer efficiency is improved, but signal misalignment occurs due to design inaccuracies, fabrication tolerances, and environmental factors
Solution Approach 1:
The patent applies preliminary action by measuring and storing propagation time values for different operating conditions (temperature, voltage, frequency) before actual data transmission. The system pre-calculates compensation values and stores them in lookup tables, so when transmission occurs, the appropriate compensation is already prepared and can be applied immediately without real-time calculation delays.
Solution Approach 2:
The system implements feedback by continuously monitoring actual signal propagation times and comparing them against stored reference values. Based on this feedback, the system dynamically adjusts delay elements to compensate for deviations caused by environmental factors, ensuring continuous optimization of signal alignment even as operating conditions change.
2Reliability
If manual compensation methods are used to adjust signal alignment, then signal synchronization is improved, but device complexity and operational overhead increase
Solution Approach 1:
The system applies self-service by automatically measuring propagation times, selecting appropriate compensation values from stored tables, and adjusting delay elements without requiring manual intervention. The apparatus autonomously adapts to environmental changes and optimizes signal alignment, eliminating the need for complex manual calibration procedures while maintaining high synchronization accuracy.
3Ease of manufacture
If fixed propagation paths are used for data and strobe signals, then routing simplicity is improved, but environmental factors cause phase skewing that limits operating frequency
Solution Approach 1:
The patent applies dynamics by making the propagation path adjustable through programmable delay elements. Instead of fixed physical routing, the system dynamically modifies the electrical path length by inserting controllable delays that can be programmed based on measured propagation characteristics. This allows the system to maintain optimal timing relationships across different operating frequencies while keeping the physical routing simple.
Data Source
AI summary
An apparatus is provided that compensates for misalignment on a synchronous data bus. The apparatus includes a replica radial distribution element, a Joint Test Action Group (JTAG) interface, and a bit lag control element. The replica radial distribution element is configured to receive a lag pulse signal, and is configured to generate a replicated strobe signal, where the replica radial distribution network includes replicated propagation path lengths, loads, and buffering of a radial distribution network for a strobe. The JTAG interface is configured to receive control information over a standard JTAG bus, where the control information indicates an amount to adjust a propagation time. The bit lag control element is configured to measure, when an update signal is asserted, the propagation time beginning with assertion of the first signal and ending with assertion of the second signal, and is configured to generate a first value on a lag bus that indicates an adjusted propagation time. The bit lag control element includes delay lock control, adjust logic, and a gray encoder. The delay lock control is configured to select one of a plurality of successively delayed versions of the first signal that coincides with the assertion the second signal, and is configured to generate a second value on a lag select bus that indicates the propagation time, where the delay lock control selects the one of a plurality of successively delayed versions of the first signal by incrementing and decrementing bus states of select inputs on a mux, and where the plurality of successively delayed versions includes inputs to the mux, and where the plurality of successively delayed versions includes outputs a first plurality of series-coupled matched inverter pairs. The adjust logic is coupled to the JTAG interface and to the lag select bus, and is configured adjust the second value by the amount prescribed by the JTAG interface to yield a third value that is output to an adjusted lag bus. The gray encoder is configured to gray encode the third value to generate the first value on the lag bus.