AN 702: Interfacing a USB PHY to the Hard Processor System USB 2.0 OTG Controller

ID 683601
Date 9/22/2017
Public
Document Table of Contents

1.3.3. Input Clock Mode

In input clock mode, the PHY receives a clock from an external source. All signals are synchronized to the clock. In this mode, a PLL in the FPGA or an external source generates the clock.
Note: For systems where the HPS must be operational before the FPGA fabric is configured, an external clock source should be used to drive the USB PHY clock. By using an external clock source, the FPGA fabric is not required to be configured before the HPS.