Flash Memory ECC Retry Signaling for Fast DDR Interfaces
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Solution Overview
Problem
Flash memory devices struggle to consistently meet the response times specified by high-speed interface protocols like DDR due to their inherently slower read latency, leading to potential processing errors when communicating with external processing systems.
Innovation Solution
A data storage device employs a memory with slow response time, using error correction coding (ECC) errors to indicate delays, allowing a processing system to manage requests through an interrupt handler that differentiates between authentic ECC errors and latency compensation responses, enabling data retrieval within the required time frames by retrying requests after a delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If flash memory devices are used to provide large storage capacity and low cost, then storage density and manufacturing cost are improved, but response time cannot consistently satisfy DDR interface protocol requirements
Solution Approach 1:
The patent introduces an intermediary mechanism (ECC error indicator) that mediates between the slow flash memory and the fast DDR interface. When flash memory cannot respond in time, the controller sends a response with an ECC error indicator to satisfy the interface timing requirement, while the actual data is retrieved later and sent in response to a retry request.
Solution Approach 2:
The patent changes the state parameter of the response by introducing an ECC error indicator flag. This allows the system to transform an invalid response (due to timing violation) into a valid response format that the DDR interface can process, while conveying information about the actual data status through the error indicator.
2Quantity of substance
If flash memory devices are used to provide large storage capacity, then storage density is improved, but response time consistency deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the processing system receives an ECC error indicator and automatically retries the request after a delay period. The system uses this feedback to determine whether to repeat the data request, creating a closed-loop control that handles timing variations reliably.
Solution Approach 2:
The patent performs preliminary action by sending a response within the required time frame even though the actual data is not yet ready. The response includes an ECC error indicator that prepares the processing system for a retry, allowing the timing requirement to be met in advance while data retrieval continues in the background.
3Ease of manufacture
If slow response memory is used to reduce cost, then manufacturing cost is improved, but interface timing compliance deteriorates
Solution Approach 1:
The ECC error indicator serves as an intermediary signal that bridges the gap between cost-effective slow memory and timing-critical fast interfaces. It allows inexpensive flash memory to appear compliant with expensive DDR interface timing requirements by providing a standardized error signal that triggers automatic retry logic.
Solution Approach 2:
The patent creates a copy mechanism where the initial response with ECC error indicator is followed by a subsequent response containing the actual data. This copying approach allows the system to satisfy timing requirements with a placeholder response while delivering the real data later in a separate transmission.
Data Source
AI summary
A method includes receiving a request to read data at a data storage device from an external device. In response to determining that the data is in a first memory of the data storage device, a first read operation is initiated to read the data from the first memory and a response is sent to the external device. The response indicates an error correction code (ECC) error. A read latency of the first read operation exceeds a reply time period corresponding to the request. The response is sent prior to completion of the first read operation and within reply time period.