Leading Zero Counter Verification Using Bit Masks and XOR Checks
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Solution Overview
Problem
Leading zero counters in computer systems are difficult to test using existing methodologies, leading to undetected faults that can cause functional errors by overestimating or underestimating the number of leading zeroes.
Innovation Solution
A system and method involving a leading zero counter and a tester that generate bit vectors and masks to verify the accuracy of leading zero counts using bitwise operations, including a half decoder and XOR gates to check for errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing testing methodologies are used on leading zero counters, then the testing process is simple, but the fault detection capability is insufficient leading to undetected faults
Solution Approach 1:
The patent introduces a tester as an intermediary component between the leading zero counter and the testing environment. This tester includes a half decoder that converts the leading zero count output into a bit mask, and XOR gates that compare this bit mask with expected values. This intermediary testing mechanism enables comprehensive fault detection without requiring complex external testing equipment, thereby improving reliability while controlling testing system complexity.
2Productivity
If a faulty leading zero counter is deployed, then the system can operate, but functional errors occur due to overestimation or underestimation of leading zeroes
Solution Approach 1:
The patent implements preliminary verification of the leading zero counter's correctness before full system deployment. The tester performs verification by generating a bit mask from the counter's output using a half decoder, then comparing this mask with expected values using XOR gates. This preliminary action ensures functional correctness is confirmed before the system operates, preventing the propagation of faults that would cause overestimation or underestimation of leading zeroes.
3Measurement precision
If comprehensive testing of leading zero counters is implemented, then fault detection improves, but the testing methodology becomes more complex
Solution Approach 1:
The patent replaces complex mechanical or manual testing methods with an electronic verification system. The tester uses a half decoder to convert the leading zero count into a bit mask representation, then employs XOR gates to perform automatic comparison with expected values. This substitution of electronic logic operations for manual or mechanical testing processes achieves precise measurement of leading zero count accuracy while reducing the difficulty of detection and measurement.
Data Source
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AI summary
Verifying the correctness of a leading zero counter, including: generating, based on an input value comprising a plurality of digits, a first bit vector, wherein each entry of the first bit vector indicates whether a corresponding digit of the input value is equal to zero; calculating, based on the first bit vector, a leading zero count for the input value; generating a bit mask comprising a number of leading ones equal to the leading zero count; generating a second bit vector comprising a one at a same index as a first occurring zero in the bit mask; and verifying the leading zero count based on the first bit vector and one or more of the bit mask and the second bit vector.