6.7. Sink Clock Tree
The IP receives DisplayPort serial data across the high-speed serial interface (HSSI). Refer to the Transceiver Reconfiguration for Different Design Variants table in the Transceiver Reconfiguration Interface section for the HSSI reference clock requirements. You can supply this frequency to the HSSI using a reference clock provided by an Altera FPGA PLL or pins.
The IP synchronizes HSSI 20-, 40-, or 32-bit data to a single HSSI[0] clock that clocks the data into the DisplayPort front-end decoder. For a detailed clock derivation of each link rate, refer to the respective design example user guide for each device.
- If rxN_vid_clk is slower than the up-stream video clock, the DCFIFO overflows.
- If the rxN_vid_clk is faster than the up-stream source video clock, the output port experiences a deassertion of the valid port on cycles in which pixel data is not available.
The optimum frequency is the exact clock rate in the up-stream source. You require pixel clock recovery techniques to determine this clock frequency.
Secondary stream data is clocked by rx_ss_clk. The sink IP also requires a 16-MHz clock (aux_clk) to drive the internal AUX controller and an Avalon clock for the Avalon® memory-mapped interface (clk).