Description
Enabling the SGMII bridge in the TSE IP results in the rate-adaptation logic being implemented in the FPGA fabric (not in the Transceiver). This means that the Ref_Clk signal must be able to connect directly to the GCLK network.
In Cyclone® IV devices REFCLK[0,1] and REFCLK[4,5] cannot connect directly to the GCLK network, hence the no fit error - Error (176559): Can't place MPLL or GPLL PLL.
Resolution
In Cyclone IV GX devices, REFCLK[0,1] and REFCLK[4,5] cannot connect directly to the GCLK network, hence if the SGMII bridge is enabled, Ref_Clk must be connected to an alternative dedicated clock input pin.
