The DDR controller for C2 for is much closer to the transceivers which
connect to the FMCp connector so designs does not have to span over all
three SLRs just over two reducing implementation and timing closure effort.
For all the Xilinx base design, define three global clock nets, which
are saved in the following three global variable: $sys_cpu_clk, $sys_dma_clk
and $sys_iodelay_clk.
These clock nets are connected to different clock sources depending of
the FPGA architecture used on the carrier. In general the following
frequencies are used:
- sys_cpu_clk - 100MHz
- sys_dma_clk - 200MHz or 250Mhz
- sys_iodelay_clk - 200MHz or 500Mhz