Bit Conversion for Direct LDPC Decoding of Defect Scan Patterns
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Solution Overview
Problem
In hard disk devices, the need to rewrite the entire surface with code words for error detection and correction during defect scanning increases inspection time and load, as conventional defect scanning patterns are not represented by code words.
Innovation Solution
A bit converter with a substitution module that converts a bit string of a predetermined pattern into a code word, using an LLR substituting circuit to correct log likelihood ratios, allowing direct LDPC decoding of defect scanning patterns without rewriting them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If defect scanning patterns are written into recording media for inspection, then defect detection capability is improved, but the patterns cannot be directly decoded by error correction decoders requiring code words
Solution Approach 1:
A bit converter is introduced as an intermediary component between the defect scanning system and the LDPC decoder. The bit converter transforms defect scanning patterns into valid LDPC code words, enabling the decoder to process scanning patterns directly without requiring separate code word writing. This mediator resolves the incompatibility between defect scanning requirements and error correction decoding requirements.
2Reliability
If the entire surface of recording media is rewritten with code words to enable error correction decoding during inspection, then error detection and correction capability is improved, but inspection time and processing load increase
Solution Approach 1:
The bit converter is configured to transform defect scanning patterns into valid LDPC code words in advance, before the decoding process. This preliminary transformation ensures that when defect scanning patterns are read from the recording media, they are already in a format suitable for LDPC decoding, eliminating the need for time-consuming rewriting operations during inspection.
3Ease of operation
If defect scanning patterns are used without conversion, then inspection process is simplified, but error correction decoding cannot be performed on the scanning patterns
Solution Approach 1:
The bit converter serves as an automatic intermediary that transparently transforms defect scanning patterns into valid LDPC code words. This transformation occurs seamlessly during the inspection process, maintaining operational simplicity while enabling error correction capability. The converter is integrated into the data processing path, requiring no manual intervention or complex procedural changes.
Data Source
AI summary
An embodiment of a bit converter includes a substitution module and an output module. The substitution module substitutes a decision result representing one of “0” and “1” for input bit information based on a substitution rule for bit information for converting a bit string of a predetermined pattern into a predetermined code word. The output module outputs the decision result of the bit information substituted by the substitution module, to a decoder configured to decode the decision result into the predetermined code word.