Hello, first thanks for the hints. I just coded the article "xl24- trouble-free switching between clocks".. First this is still clock gating, but with glitches removed. XST still sees it as being combinational. I think this would fit my application, where I made a 14-bit counter work in one case, clocked by 5.37mhz, and in the other case at 1.79mhz.
What happens when I put the attribute clock_source in the vhdl code? is it just to remove the warning from xst, or will it, by some sort of magic, route the output from the "clock selector" block, to the clock routing in my FPGA?
And to the question of Peter, I need to be able to switch between clocks arbitrarily, while the counter still holds the count, and hence incrementing at the new rate.
Thanks so much for the hints! Jac