9.4.2. Clocks and Reset
The PCI Express Base Specification requires an input reference clock, which is called refclk in this design. The PCI Express Base Specification stipulates that the frequency of this clock be 100 MHz.
The PCI Express Base Specification also requires a system configuration time of 100 ms. To meet this specification, IP core includes an embedded hard reset controller. This reset controller exits the reset state after the periphery of the device is initialized.