Hi, I'm Mark and I'm a VHDL newbie. I need to generate 2 different signals from a 100 Mhz clock: The first one will have 78 Mhz frequency and 50% Duty Cycle. The second one 78 Mhz f and 70% DC. I can't use DCM for this, just counters. I attached a vhd source with a clock filter, I used this to get a 25 Mhz signal from a 100 Mhz clock with 50% D.C. It works fine, but it won't work as expected if the division between frequency_in and frequency_out is near 1, like in the 100/78 case.
Clocks in FPGAs are generated by clock managers. Always. That jittery derivative (named clock_out in your case) generated with a counter may be used as clock enables, but never ever as real clock. Just read the manual of your FPGA. Chapter "Clocking".