Dynamic Memory Refresh Controller Using Priority-Based Request Scheduling

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Solution Overview

Problem

Conventional dynamic memory refresh controllers face challenges in optimizing the refresh trigger interval, leading to excessive power consumption and potential data loss due to frequent refresh operations, which collide with normal access operations and fail to maintain data integrity within the specified maximum refresh interval (tREFImax).

Innovation Solution

A dynamic memory refresh controller comprising a FIFO memory, scheduler, and signal generator that reorders requests based on priority and idle states of memory banks, using a finite state machine and tREF counter to determine optimal refresh timing, thereby maximizing the refresh interval and reducing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If refresh operations are performed frequently to ensure data preservation within tREFImax, then data integrity is maintained, but power consumption increases

Engineering Contradiction:

Improvedata integrityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The refresh controller dynamically adjusts the refresh trigger interval based on the current state of memory banks. When banks are in idle state, the controller extends the refresh interval beyond the conventional fixed timing, thereby reducing refresh frequency and power consumption while still ensuring data integrity through timely refreshes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the refresh interval parameter from a fixed value to a variable value that adapts to memory bank states. The controller monitors bank availability and adjusts the refresh trigger timing accordingly, allowing longer intervals when banks are idle and shorter intervals when banks are busy, thus optimizing power consumption while maintaining data preservation.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If refresh trigger interval is extended to reduce power consumption, then power efficiency improves, but data may be lost if interval exceeds tREFImax

Engineering Contradiction:

Improvepower consumptionVSAvoiddata preservation

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The refresh controller implements a feedback mechanism that continuously monitors the state of memory banks and adjusts refresh timing based on this information. The controller receives feedback about bank idle/busy states and uses this feedback to dynamically determine the optimal refresh trigger interval, ensuring it never exceeds tREFImax while maximizing power efficiency.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The controller performs preliminary assessment of memory bank states before issuing refresh triggers. By checking whether banks are in idle state in advance, the controller can safely extend the refresh interval knowing that data will be preserved, thus reducing power consumption without compromising data integrity.

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If refresh operations are performed at fixed intervals, then implementation is simple, but refresh may collide with read/write operations causing performance degradation

Engineering Contradiction:

Improvecontroller complexityVSAvoidmemory access speed

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The refresh controller transitions from static fixed-interval refresh to dynamic state-dependent refresh timing. By making refresh timing adaptive to memory bank states, the system avoids collisions with read/write operations while maintaining reasonable controller complexity through state monitoring and conditional trigger generation.

Inventive Principle:

Principle #15Dynamics

4Reliability

If refresh trigger occurs immediately when tREFI minimum time is met, then data preservation is ensured, but refresh frequency increases causing higher power consumption

Engineering Contradiction:

Improvedata preservationVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Before issuing a refresh trigger, the controller performs a preliminary check to determine if memory banks are in idle state. This preliminary action allows the controller to extend the refresh interval beyond the minimum tREFI time when conditions permit, thereby reducing refresh frequency and power consumption while still ensuring data preservation through timely refreshes when banks become available.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7603512B2Dynamic memory refresh controller, memory system including the same and method of controlling refresh of dynamic memory

Publication Date: 2009.10.13 SAMSUNG ELECTRONICS CO LTD

AI summary

A dynamic memory refresh controller includes a first in first out (FIFO) memory, a scheduler, a refresh control unit, and a signal generator. The FIFO memory stores and manages requests from a master device. The scheduler reorders the requests from the master device based on priorities assigned to the master device or provides information about following requests. The refresh control unit determines a refresh timing of the dynamic memory based on the existence of the following requests and an idle state of banks constituting the dynamic memory. Accordingly, the dynamic memory refresh controller may maximize a refresh trigger interval by changing the management order of the requests from the master device based on the priority of the response latency.