DQS Gate - 1.0 English

Versal ACAP Programmable Network on Chip and Integrated Memory Controller LogiCORE IP Product Guide (PG313)

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1.0 English

The internal clock strobe is adjusted to align with the DQS returning from the memory. This is performed on all byte lanes in parallel.

This is accomplished as follows:

  1. Search for the 3rd DQS edge using the initial read latency setting -2 and incrementing coarse taps.
  2. Search for the noise region using fine taps, and then center on the noise region.
  3. Adjust the read latency setting (+2) to restore alignment with the first DQS edge as well as account for the detected preamble type (1 or 2 TCK).
  4. Repeat for each memory rank.
  5. Adjust the coarse and read latency values to account for the longest delay of all the ranks.
Table 1. DQS Gate Registers
Register Name Quantity Description
Fx_DQSGATE_STG1_OVERFLOW Rank and Byte 1 of 16 coarse taps have been used to find the 3rd DQS edge
Fx_DQSGATE_STG1_READ_LAT Rank and Byte The read latency value after centering on the noise region
Fx_DQSGATE_STG1_RLDLYRNK_CRSE Rank and Byte The coarse tap value for the 3rd DQS edge
Fx_DQSGATE_STG1_RLDLYRNK_FINE Rank and Byte The fine tap value for the 3rd DQS edge
Fx_DQSGATE_STG2_READ_LAT Rank and Byte Read Latency after adjusting for Preamble type (1 or 2TCK)
Fx_DQSGATE_STG2_RLDLYRNK_CRSE Rank and Byte The coarse tap value after adjusting for Preamble type
Fx_DQSGATE_MAX_READ_LAT 1 The largest read latency value for all calibrated ranks. For a single rank interface, this value will match DQSGATE_STG2_READ_LAT
Fx_DQSGATE_READ_LAT_FINAL Byte Final Read Latency value
Fx_DQSGATE_RLDLYRNK_CRSE_FINAL Rank and Byte Final coarse tap value