DLL-Based Strobe Receiver Lockout for Bus Noise Rejection
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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 processes, leading to substandard error correction and increased system costs due to worst-case scenario design.
Innovation Solution
A dynamic lockout mechanism using a delay-locked loop (DLL) that continuously updates the lockout time period based on variations in bus clock frequency, voltage, and temperature, employing a 64-tap delay element and encoded select vector signals to determine the optimal lockout time for source synchronous strobe receivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed logic mechanisms are used for receiver lockout, then the lockout time can be calculated deterministically, but the lockout time cannot adapt to variations in bus clock frequency, voltage, temperature, and fabrication processes
Solution Approach 1:
The patent implements a dynamic lockout time mechanism using a delay-locked loop (DLL) that continuously adjusts the lockout period based on actual operating conditions. The DLL measures the actual bus clock period and dynamically configures the lockout time accordingly, allowing the system to adapt to variations in frequency, voltage, and temperature while maintaining reliable error correction
Solution Approach 2:
The patent changes the lockout time parameter dynamically based on measured operating conditions. By monitoring actual bus clock frequency and adjusting the lockout period as a corresponding parameter, the system maintains optimal error correction capability across different operating scenarios without being constrained by fixed logic calculations
2Reliability
If worst-case scenarios are used for lockout time design, then the system can handle all possible variations, but the design becomes overly conservative and increases system cost
Solution Approach 1:
The system performs self-characterization during initialization by automatically measuring its own delay elements and clock periods under actual operating conditions. This self-service approach eliminates the need for external worst-case scenario specifications, allowing the system to configure optimal lockout times based on its own measured characteristics, thereby reducing conservative design margins and fabrication costs
3Reliability
If the lockout time is extended to cover all possible glitch scenarios, then more errors can be prevented, but legitimate data transfers may be blocked
Solution Approach 1:
The patent uses dynamic adjustment of lockout time based on the measured bus clock period and actual operating conditions. By continuously adapting the lockout duration to match the actual timing characteristics, the system prevents glitches effectively while avoiding excessive lockout periods that would block legitimate data transfers, thereby maintaining high productivity
Data Source
AI summary
An apparatus for locking out a source synchronous strobe receiver, including a delay-locked loop (DLL) and one or more receivers. The DLL receives a reference clock, and generates a select vector and an encoded select vector that both indicate a lockout time. The select vector is employed to select a delayed version of the reference clock that lags the reference clock by the lockout time. The lockout time is slightly less than a number of cycles of the reference clock. The one or more receivers are each coupled to the delay-locked loop. Each of the one or more 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 to determine the lockout time by selecting a delayed version of the corresponding strobe.