Clock Glitch Detection Circuit With Shift-Register Comparison
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Solution Overview
Problem
Clock glitches caused by radiation, cosmic rays, or alpha particles can lead to timing errors in computer logic circuits, affecting phase locked loop circuits and other timing-dependent systems.
Innovation Solution
A clock glitch detector circuit comprising a phase locked loop, shift register, and latches to store and compare clock signals, detecting glitches through OR logic output, with a clock switch to alternate to a backup clock when glitches are identified.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clock glitch detector circuit is implemented to detect timing errors, then the reliability of the system is improved, but the device complexity increases due to additional components like shift registers, latches, and OR logic
Solution Approach 1:
The clock glitch detector is divided into distinct functional modules: a shift register for storing clock values, latches for retrieving and comparing bits, and OR logic for determining glitches. This segmentation allows each component to perform a specific function, improving reliability while managing complexity through modular design.
Solution Approach 2:
The shift register acts as an intermediary component that stores current and previous clock values, enabling comparison without directly modifying the clock signal path. This intermediary structure detects glitches indirectly by comparing sequential states, maintaining system reliability while adding minimal complexity.
2Measurement precision
If multiple latches and comparison logic are added to detect clock glitches, then the measurement precision of timing errors is improved, but the loss of time increases due to additional processing steps
Solution Approach 1:
The shift register continuously stores sequential clock values in advance, preparing data for comparison before a glitch detection event occurs. This preliminary storage eliminates the need for complex real-time sampling logic, achieving high measurement precision while minimizing detection processing time.
Solution Approach 2:
The circuit compares only critical bit positions (current vs. previous clock states) rather than analyzing the entire clock waveform. This partial comparison approach achieves sufficient glitch detection accuracy while significantly reducing processing time compared to comprehensive waveform analysis.
Data Source
AI summary
Embodiments herein describe a glitch detector circuit (and method of operation) for detecting glitches in a clock signal. In one embodiment, the glitch detector includes a shift register that samples the reference clock using a clock signal output by a PLL. The value in a first memory element of the shift register can be sampled to previous values that were stored (and then bit shifted) in the shift register. If there is a mismatch, the glitch detector indicates there was a clock glitch in the reference clock, and a corrective action can be performed.