Boot ROM Read Retry Sequences via External NVM

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Solution Overview

Problem

Nonvolatile memory devices, such as flash memory, face reliability issues as the number of program/erase cycles increases, and existing error correction methods struggle to correct errors, necessitating read retry operations that are manufacturer-specific and cannot be updated without modifying the boot ROM.

Innovation Solution

A memory system with a memory controller and external non-volatile memory that includes a read retry register and table, allowing for multiple read retry sequences without updating the boot ROM code, enabling flexible retry operations by storing and executing retry sequences in the external NVM.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a boot ROM is used to support read retry sequences, then read retry operations can be executed, but the system cannot adapt to newly introduced read retry sequences without modifying the boot ROM code

Engineering Contradiction:

Improveadaptability to new read retry sequencesVSAvoidboot ROM code modification requirement

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent divides the read retry sequence storage into two segments: a fixed boot ROM that contains the execution engine and a flexible external NVM that stores the actual retry sequences. This segmentation allows the boot ROM to remain unchanged while the external NVM can be updated with new sequences, resolving the contradiction between adaptability and device complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary structure (the external NVM with read retry table) that mediates between the boot ROM execution engine and the actual retry sequence data. This intermediary allows the system to execute new sequences without modifying the boot ROM code, as the boot ROM simply reads and executes instructions from the external NVM.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If manufacturer-specific read retry sequences are used, then errors can be corrected for specific devices, but the system lacks flexibility to support multiple different sequences

Engineering Contradiction:

Improveerror correction capabilityVSAvoidsupport for multiple read retry sequences

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent makes the boot ROM execution engine universal by designing it to read and execute read retry sequences from an external NVM. This allows a single boot ROM to support multiple different manufacturer-specific sequences without needing separate boot ROMs for each manufacturer, achieving both reliability through manufacturer-specific sequences and versatility through multi-sequence support.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9785382B2Method and apparatus for read retry sequence for boot ROM

Publication Date: 2017.10.10 NXP USA INC

AI summary

A memory system capable of running a variety of different read retry sequences includes a memory controller that has a boot ROM with stored code for executing a read retry sequence. A non-volatile memory device such as a NAND flash includes a read retry register and receives command instructions including a read retry instruction from the memory controller and in response provides read data. A second non-volatile memory that is external to the NAND flash has a read retry table describing read retry sequence items that include a command, a read retry register address, and read retry data for updating the read retry register.