On-Die ECC Memory Layout for Poison Flag Storage Without Overhead
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Solution Overview
Problem
Dynamic random access memories (DRAMs) face increasing bit errors and yield decreases due to shrinking fabrication design rules, necessitating effective error correction mechanisms without incurring size overhead.
Innovation Solution
A semiconductor memory device and system that incorporates an on-die error correction code (ECC) engine and control logic circuit, capable of storing a poison flag in a parity cell region without size overhead, by selectively replacing parity data with the poison flag during write operations and performing ECC encoding and decoding based on a poison mode signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error correction mechanisms are added to DRAMs to address increasing bit errors, then reliability is improved, but device complexity and size overhead increase
Solution Approach 1:
The patent merges the poison flag storage function with the existing parity cell region structure. Instead of adding separate storage resources for poison flags, the invention utilizes the already-dedicated parity cells to store both parity data and poison flag information, thereby improving reliability without increasing device complexity or size overhead.
Solution Approach 2:
The parity cell region is designed to serve multiple functions: storing traditional parity data for error detection and simultaneously storing poison flag metadata for poisoned data identification. This multi-functional approach allows the same hardware resources to support both error correction and poison flag management, resolving the contradiction between reliability improvement and complexity increase.
2Reliability
If poison flag metadata is stored in separate memory resources, then reliability is improved through better error tracking, but memory capacity is reduced due to size overhead
Solution Approach 1:
The invention combines poison flag storage with parity cell storage, merging two functions into a single storage resource. The parity cell region simultaneously holds parity bits and poison flag metadata, eliminating the need for separate poison flag storage resources and thus preventing any reduction in usable memory capacity.
Solution Approach 2:
The poison flag information is nested within the existing parity cell structure. Instead of adding external storage, the patent embeds the poison flag metadata inside the same storage units (parity cells) that already contain parity data, allowing dual functionality without additional space consumption.
Data Source
AI summary
A semiconductor memory device includes a memory cell array, an on-die error correction code (ECC) engine, and a control logic circuit. The on-die ECC engine, based on an ECC, in a write operation, performs an ECC encoding on main data to generate first parity data, selectively replaces a portion of the first parity data with a poison flag to generate second parity data based on a poison mode signal, provides the main data to a normal cell region in a target page of the memory cell array, and provides the first parity data to a parity cell region in the target page or provides the poison flag and the second parity data to the parity cell region. The control logic circuit controls the on-die ECC engine and generates the poison mode signal, based on a command and an address from a memory controller.