Change a clock frequency

[ack05]

Hi!

I use an FPGA 'xc7a35tcpg236-1' on BASYS3 with Vivado 2019.1 and Verilog.

I want to change a clock frequency from 100MHz to other frequencies, but the frequencies are difficult to generate by using counters. (ex. 13.56MHz, 33.33MHz)

Does anyone know how to generate these frequencies?

[andrewlan · Accepted solution]

Use one of the on chip MMCM's.

See this doc for detail on this block:

https://www.xilinx.com/support/documentation/user_guides/ug472_7Series_Clocking.pdf

To add one into your design you can use the clocking wizard IP located in Vivado's IP Catalog whcih provides a strait forward user interface. See:

https://www.xilinx.com/support/documentation/ip_documentation/clk_wiz/v6_0/pg065-clk-wiz.pdf