Cyclone V Gbx Transceivers - can't fit more than 4, should be able to use 6? Error (14566): The Fitter cannot place 5 periphery component(s) due to conflicts with existing constraints (5 Channel PLL(s)).

​Hi,

As I look into your design, I can replicate the Fitter error when compiling your design. I notice that you have placed channels to physical channel of CH 1 and CH4 in the design. For your information, the CMU PLL is only available in physical CH1 and CH4. Therefore, you would need to leave either one of these two CHs unused for CMU PLL purpose. This also explain why when you leave AB2/1 and Y2/1 unused, the design can pass Fitter compilation. Note that if you leave K2/1 and H2/1 unused, your design will also pass compilation since there is one CMU PLL here as well.

Please let me know if there is any concern. Thank you.