Margin tool for double data rate memory systems

Abstract

A tool for testing a double data rate ('DDR') memory controller to ensure that data strobe transitions are aligned with data eyes to achieve a desired data integrity during data transfers between the memory controller and the memories. After the memory controller completes its training sequence during the initialization process, the tool sweeps the data strobe transition across the data eye. At each timing step during the sweep, several tests may be conducted to check for integrity of functionality. The tool thus generates a pass/fail margin table. The locations of the data strobe transitions selected by the memory controller during its previously run training sequence are then added to this tool-generated margin table. The result is essentially a pseudo data eye, reconstructed including the data strobe transition with the data eye. An inspection of the location of the data strobe transition with the data eye may be utilized to show the range of timing steps available before the data strobe transition would fail to capture valid data from the incoming data eye.