Gray-Coded Strobe Receiver Lockout for Adaptive Timing
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Solution Overview
Problem
Conventional receiver lockout techniques for source synchronous strobe signals in microprocessor systems are inadequate as they do not account for variations in bus clock frequency, voltage, temperature, and fabrication process variations, leading to substandard error compensation and potential inadvertent enablement due to spurious noise.
Innovation Solution
A dynamic lockout mechanism utilizing a delay-locked loop (DLL) with a gray encoder to continuously update the lockout time period, accounting for variations in bus clock frequency, voltage, and temperature, and incorporating a 64-tap delay element to select the appropriate delayed versions of the reference clock signal for precise lockout timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed logic mechanisms are used to calculate lockout time, then the lockout time calculation is simple, but the lockout time is adversely affected by operating parameter changes such as bus clock frequency variations, temperature variations, voltage variations, and fabrication process variations
Solution Approach 1:
The patent implements a dynamic lockout time adjustment mechanism using a delay-locked loop (DLL) that continuously adapts the lockout time period based on real-time operating conditions. The DLL receives a reference clock signal and generates delayed versions of this signal, allowing the lockout time to be dynamically adjusted in response to frequency, temperature, and voltage variations, thereby resolving the contradiction between simple fixed logic and accurate adaptive timing.
Solution Approach 2:
The patent changes the timing parameters of the lockout mechanism by using a 64-tap delay element that can select different delay values. An adjustment mechanism modifies the lockout time period by changing the selected delay tap based on operating conditions, enabling the system to adapt to fabrication process variations and environmental changes while maintaining reliable error detection.
2Reliability
If worst-case scenarios are employed in fixed lockout time design, then the design is robust against variations, but the lockout time may be excessively long reducing system productivity
Solution Approach 1:
The DLL-based adjustment mechanism enables the lockout time to be dynamically optimized rather than statically set to worst-case values. The system can use shorter lockout times when operating conditions permit, improving throughput while maintaining sufficient error detection capability, thus resolving the trade-off between robustness and productivity.
Solution Approach 2:
By implementing adjustable delay taps in the DLL, the patent allows the lockout time parameter to be optimized for different operating conditions. The adjustment mechanism selects appropriate delay values that provide adequate error detection without imposing excessive delays, thereby improving system productivity while maintaining reliability.
3Device complexity
If the lockout time period is not dynamically adjusted, then the mechanism is simple to implement, but it cannot compensate for fabrication process variations and environmental changes
Solution Approach 1:
The patent introduces a dynamic adjustment mechanism that modifies the lockout time period based on real-time operating conditions including temperature, voltage, and frequency variations. The DLL continuously adapts the timing parameters, enabling the simple lockout mechanism to gain adaptability without significantly increasing overall system complexity.
Solution Approach 2:
The adjustment mechanism operates autonomously to compensate for fabrication process variations and environmental changes. The DLL automatically adjusts the lockout time based on feedback from operating conditions, enabling the system to self-correct without external intervention, thus providing adaptability while maintaining implementation simplicity.
4Device complexity
If conventional fixed lockout techniques are used, then the implementation is straightforward, but erroneous receptions due to bus noise and spurious signals cannot be reliably prevented
Solution Approach 1:
The patent implements a dynamic lockout time adjustment using DLL that adapts to real-time operating conditions, enabling more reliable prevention of erroneous receptions caused by noise and glitches. The dynamic timing ensures that the lockout period is always appropriate for current conditions, improving error prevention capability beyond what fixed implementations can achieve.
Solution Approach 2:
The adjustment mechanism incorporates feedback from operating conditions (frequency, temperature, voltage) to continuously optimize the lockout time period. This feedback loop ensures that the lockout mechanism remains effective under varying conditions, reliably preventing erroneous receptions while maintaining straightforward implementation through the use of standard DLL components.
Data Source
AI summary
An apparatus for locking out a source synchronous strobe receiver, including a delay-locked loop (DLL) and receivers. The DLL receives a reference clock, and generates a select vector and an encoded select vector. The select vector is employed to select a delayed version of the reference clock that lags the reference clock by a prescribed number of cycles. The select vector is reduced by an amount and is gray encoded to indicate the lockout time. The receivers are each coupled to the delay-locked loop. Each of the receivers receives the encoded select vector and a corresponding strobe, and locks out reception of the corresponding strobe for the lockout time following transition of the corresponding strobe. The encoded select vector is employed by a gray code mux therein to determine the lockout time by selecting a delayed version of the corresponding strobe.