Parallel Test Path for Dynamic Signal Quality Measurement
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Solution Overview
Problem
Existing methods for determining signal quality in digital systems, particularly for clocked signals applied to chip receivers, are time-consuming and disruptive, often requiring systems to be taken offline for testing, and struggle to efficiently measure signal margins and clock skew without affecting normal operation.
Innovation Solution
A processor configuration with both a normal and test path, where the test path uses a variable voltage reference and selectively skewed clock signal to simulate error conditions without affecting the normal data flow, allowing for continuous testing of signal quality and clock skew margins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional oscilloscope-based measurement methods are used to test signal quality, then measurement precision can be achieved, but the testing process becomes extremely time-consuming and requires systems to be taken offline
Solution Approach 1:
The patent creates a test path that is a copy of the normal data path, using duplicate buffers and latches. This test path processes test data alongside normal data, allowing signal quality measurements to be performed on the copied path without affecting the original operational path, thereby enabling continuous operation during testing
Solution Approach 2:
The system is divided into separate normal and test paths. The test path includes dedicated test buffers and latches that can be independently controlled and measured. This segmentation allows simultaneous operation of normal data processing and test measurements without mutual interference, reducing testing time while maintaining precision
2Reliability
If traditional measurement methods are applied to ensure signal quality compliance, then device reliability is maintained, but normal system operation is disrupted and requires retransmission or reboot
Solution Approach 1:
The patent introduces a test path as an intermediary that handles all measurement and testing functions. This test path acts as a mediator between the normal operational path and the measurement requirements, allowing signal quality verification without directly interfering with normal data flow. The test path absorbs the measurement burden, protecting the operational path from disruption
Solution Approach 2:
The system performs preliminary testing through the test path before actual errors occur in normal operation. By continuously monitoring signal quality margins through the test path, potential issues are detected and can be addressed before they cause system failures, retransmissions, or reboots, thereby maintaining both reliability and productivity
3Measurement precision
If comprehensive signal measurements are performed on all chip signals, then complete quality assurance is achieved, but the complexity of the testing system increases significantly
Solution Approach 1:
The test path components (test buffers, test latches, XOR gates) serve multiple functions: they process test data, measure signal quality margins, detect errors, and verify clock skew tolerances. This multi-functionality reduces the need for separate dedicated measurement equipment for each function, simplifying the overall testing system while maintaining comprehensive verification capabilities
Data Source
AI summary
A receiving processor is configured with a normal (operational) path and a test path. The test path is configured in parallel with the normal path. The test path simulates and receives as input the same data as the normal path, but the test path has a separate voltage reference (Vref<sub2>—</sub2>test) which is applied to a test input buffer. The same data input to normal buffer is also input to the test buffer. The output of the test buffer is input to a test latch. A clocking signal supplied to the test latch is a variable clocking signal enabling the clock signal to be skewed selectively. The output of the test latch is compared with the output of the normal latch, and differences between the two output signals defines an error for a particular voltage/clock-skew combination.