Cyclone® V Device Handbook: Volume 1: Device Interfaces and Integration

ID 683375
Date 10/18/2023
Document Table of Contents Update Enable Circuitry

The update enable circuitry enables the registers to allow enough time for the DQS delay settings to travel from the DQS phase-shift circuitry or core logic to all the DQS logic blocks before the next change.

Both the DQS delay settings and the phase-offset settings pass through a register before going into the DQS delay chains. The registers are controlled by the update enable circuitry to allow enough time for any changes in the DQS delay setting bits to arrive at all the delay elements, which allows them to be adjusted at the same time.

The circuitry uses the input reference clock or a user clock from the core to generate the update enable output. The UniPHY intellectual property (IP) uses this circuit by default.

Figure 132. DQS Update Enable WaveformThis figure shows an example waveform of the update enable circuitry output.