Read Centering (Complex) - 1.0 English

The final stage of DQS read centering that is completed before normal operation repeats the steps performed during MPR DQS read centering but with a difficult/complex data pattern. The purpose of using a complex pattern is to stress the system for SI effects such as ISI and noise while calculating the read DQS center position. This ensures that the read center position can reliably capture data with margin in a true system.

This is accomplished as follows:

1. Reset PQTR and NQTR delays to 0 and verify that data is being properly read.
2. Delay the DQ/DBI until the noise region is found. Use short read bursts until noise region is found, then use long reads for accurate edge detection.
3. Delay the clock strobe to return to the valid region, continue until the noise region on the other side is found. Use short read bursts until noise region is found, then use long reads for accurate edge detection.
4. Center the strobe in the valid region.