220.127.116.11. Delay-Locked Loop
The delay-locked loop (DLL) uses a frequency reference to dynamically generate control signals for the delay chains in each of the DQS pins, allowing the delay to compensate for process, voltage, and temperature (PVT) variations. The DQS delay settings are gray-coded to reduce jitter if the DLL updates the settings.
There are a maximum of four DLLs, located in each corner of the Cyclone® V devices. You can clock each DLL using different frequencies.
The DLLs can access the two adjacent sides from its location in the device. You can have two different interfaces with the same frequency on the two sides adjacent to a DLL, where the DLL controls the DQS delay settings for both interfaces.
I/O banks between two DLLs have the flexibility to create multiple frequencies and multiple-type interfaces. These banks can use settings from either or both adjacent DLLs. For example, DQS1R can get its phase-shift settings from DLL_TR, while DQS2R can get its phase-shift settings from DLL_BR.
The reference clock for each DLL may come from the PLL output clocks or clock input pins.
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