You can specify the DCLK frequency for the AS configuration in the Quartus® Prime configuration settings.
Select Assignments menu ⇒ Device ⇒ Device and Pin Options ⇒ Configuration and set the Configuration scheme to Active Serial.
After that, specify the clock source from the list of Active serial clock sources.
After completing the configuration, compile the device.
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Category: Specification
Tool: Quartus® Prime
Device: Stratix® V / Arria® V / Cyclone® V