There are two clock domains within the PCIe PHY:
- PCIe_PHY PIPE port clock domain (PIPE_PCLK and PIPE_MCLK), where 32/16 bit-data is transferred between PCIe_SS controller and PCIe_PHY
- txclk/rbclk functional clock domain in which PCIe PHY generates clock: txclk for 10-bit parallel data transmission, and recovers the rbclk from serially received data.