Willard

The Arty-S7 documentation says there is a 12 MHz system clock on FPGA pin F14, but as a posting here pointed out last December, there is no such oscillator. The oscillator position on the board is unpopulated, and the recommendation is to use the DDR clock as a clock source instead of the system clock. Nonetheless, the board file says there is a 12 MHz clock named CLK12MHZ on pin F14, and I have used CLK12MHZ in a simple design and it worked as expected. How is that happening? I can't figure out any clock source.