LDPC ERASURE DECODING FOR FLASH MEMORIES

摘要

A Solid-State Disk (SSD) controller uses LDPC decoding to enable flash memory accesses with improved latency and/or error correction capabilities. With SLC flash memory having a BER less than a predetermined value, the SSD controller uses a 1-bit read (single read) hard-decision LDPC decoder to access the flash memory. If the hard-decision LDPC decoder detects an uncorrectable error, then the SSD controller uses a 1.5-bit read (two reads) erasure-decision LDPC decoder to access the flash memory. With flash memory having a raw BER between two other predetermined values, the SSD controller omits the use of the hard-decision LDPC decoder and uses only the erasure -decision LDPC decoder to access the flash memory. Variations of the SSD controller similarly access MLC flash memory. Some SSD controllers dynamically switch between hard-decision and erasure -based decoders based on dynamic decoder selection criteria.