Cyclone® V Hard Processor System Technical Reference Manual

ID 683126
Date 8/28/2023
Public
Document Table of Contents

19.4.4.1. Reset Requirements

There must be a minimum of 12 cycles on the ulpi_clk clock before the controller is taken out of reset. During reset, the USB OTG controller asserts the ulpi_stp signal. The PHY outputs a clock when it sees the ulpi_stp signal asserted. However, if the pin multiplexers are not programmed, the PHY does not see the ulpi_stp signal. As a result, the ulpi_clk clock signal does not arrive at the USB OTG controller.

Software must ensure that the reset is active for a minimum of two usb_mp_c lk cycles. There is no maximum assertion time.