DDR Memory Controller Timing Alignment via Dynamic Delay Adjustment
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Solution Overview
Problem
In DDR systems, ensuring memory access alignment becomes increasingly challenging as DRAM speeds increase, leading to higher likelihoods of clock edge crossings, which can result in data capture issues during read and write operations.
Innovation Solution
A memory controller executes write and read operations in a DDR memory module, signaling these operations and sending data with a data strobe signal, and determines read and write adjust values based on captured data to align operations correctly, adjusting latency intervals to ensure proper timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DRAM speed is increased to improve data transfer rate, then productivity is improved, but the likelihood of clock edge crossings increases causing data capture issues
Solution Approach 1:
The patent implements dynamic delay adjustment mechanisms where the memory controller continuously measures actual data arrival times and adjusts DQS and DQ delays in real-time based on observed timing variations. This dynamic adaptation allows the system to maintain reliable data capture despite increased DRAM speeds that push operations closer to clock edge boundaries.
Solution Approach 2:
The training sequence incorporates feedback loops where DQS and DQ arrival times are measured against reference clocks, and these measurements feed back into delay adjustment circuits. This feedback mechanism enables automatic correction of timing skew caused by higher DRAM speeds, ensuring data is captured at optimal moments relative to clock edges.
2Reliability
If delay adjustment is increased to ensure proper timing alignment, then reliability is improved, but latency between signaling and data capture increases
Solution Approach 1:
The patent employs parameter changes by adjusting delay values in fine increments based on measured timing skew. Rather than applying fixed large delays, the system dynamically modifies delay parameters to the minimum necessary amount, achieving timing alignment while minimizing additional latency introduced by delay circuits.
Solution Approach 2:
The training sequence performs preliminary delay measurements and adjustments before actual data transfer operations begin. By pre-characterizing timing relationships and pre-adjusting delays during initialization, the system establishes optimal timing parameters in advance, avoiding the need for excessive delays during active data transfer.
Data Source
AI summary
Memory access alignment in a double data rate (‘DDR’) system, including: executing, by a memory controller, one or more write operations to a predetermined address of a DDR memory module, including sending to the DDR memory module a predetermined amount of data of a predetermined pattern along with a data strobe signal; executing, by the memory controller, a plurality of read operations from the predetermined address of the DDR memory module, including capturing data transmitted from the DDR memory module; and determining, by the memory controller, a read adjust value and a write adjust value in dependence upon the data captured in response to the read operations.