Is it possible to use a target clock rate less than 5mhz? If so what are the settings required to set, say, a 1mhz clock?
In theory, 10 MHz is the lowest supported clock rate. That’s what’s advertised here: Overview & Comparison - NewAE Hardware Product Documentation
In practice most of our example notebooks run at 7.37 MHz and even 5 MHz seems to work fine. We don’t support generating a clock below 5 MHz.
That is because one of the clocking elements in Husky is the FPGA MMCM, which has a minimum frequency rating of 10 MHz:
(from the Xilnx DS181 Artix7 data sheet)
If you need to clock your target below that, one solution is to use a external PLL which takes the Husky-generated clock and divides it down to your desired frequency.
Thanks for the detailed answer! Are there issues using an external clock with the Husky at <5mhz?
Yes, for the same reason; in this situation the target clock is feeding the FPGA’s PLLs, and those need >= 10 MHz (though again in practice down to 5 MHz seems to work fine).
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Thank you for your answer and time!