Programmable Delay Elements for Dual-Port SRAM Timing Control
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Solution Overview
Problem
As semiconductor fabrication processes advance, the accuracy of mathematical models used in manufacturing FPGAs decreases, leading to degradation of timing margins and performance metrics, which can result in functional failures in dual-port SRAMs embedded in programmable ICs.
Innovation Solution
Incorporating a multitude of programmable delay elements along critical signal paths to control the timing of read, write, and read-then-write operations in dual-port SRAMs, allowing for coarse and fine adjustments of signal timings to maintain optimal timing margins between clock signals and ensure accurate memory access operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If semiconductor fabrication processes advance to increase transistor density, then the number of transistors on IC increases, but the accuracy of mathematical models used in manufacturing decreases leading to timing margin degradation
Solution Approach 1:
The patent introduces programmable delay elements that allow dynamic adjustment of timing parameters (delays) for critical signals. By changing the delay parameters of clock signals and memory control signals, the system compensates for timing margin degradation caused by fabrication process variations and modeling inaccuracies, thereby maintaining reliable memory operation despite increased transistor density
Solution Approach 2:
The patent implements dynamically adjustable delay elements that can be programmed to provide different delay values. This dynamic adjustment capability allows the system to adapt timing margins in real-time based on actual process variations, replacing static timing designs with flexible, programmable timing control to overcome the limitations of fixed mathematical models
2Reliability
If programmable delay elements are added to control timing margins, then reliability of memory operations improves, but device complexity increases
Solution Approach 1:
The patent designs delay elements that can be universally applied to multiple critical signals (clock signals, row select signals, column select signals, sense amplifier enable signals) within the memory system. These multi-functional delay elements provide timing adjustment for various memory operations (read, write, read-then-write) without requiring separate control circuits for each signal, thereby improving reliability while limiting the increase in overall device complexity
3Productivity
If timing margins are adjusted to prevent functional failures, then yield increases, but the number of programmable elements increases
Solution Approach 1:
The patent segments the timing control function into multiple independent programmable delay elements distributed throughout the memory system. Each delay element handles a specific critical signal path, allowing for localized timing adjustments. This segmentation enables precise control of timing margins without requiring a single complex global control mechanism, thereby improving yield while managing the number of programmable elements through functional distribution
Data Source
AI summary
A dual-port static random access memory (SRAM) includes a multitude of programmable delay elements disposed along the paths of a number signals used to carry out read, write or read-then-write operations. At least one of the programmable delay elements controls the timing margin between a pair of clock signals that trigger a read/write enable signal. A second programmable delay element coarsely adjusts the delay of a first signal associated with a dummy bitline. A third programmable delay element finely adjusts the delay of a second signal associated with the dummy bitline. A fourth programmable delay element controls the delay of a signal used to reset the read/write enable signal. During a read operation, the voltage level of the second signal is used as an indicator to activate the sense amplifiers. During a write operation, the voltage level of the second signal is used to control the write cycle.