You are right, it would work on a Spartan-3E (FCLKOUT_MIN = 5 MHz) but not on a Spartan-3 (FCLKOUT_MIN = 18 MHz).
Fortunately there is very simple solution: configure the first DCM with 8/1 multiply rate (fclkout = 35.468952 MHz) and the second one with 15/19 (fclkout = 28.001804 MHz). It should work, please try it.
Yes, it works.fH: 31.2 KHz fV 50.1 Hz But now the next problem occured. Tape loading via Joystickport still doesn´t work. I have connected the headphone output to joystickport 2 Pin 9 (Fire2) .
I can see the fpga port received something but no audio signals. While loading the border of the screen flashes sometimes.
The Joystickport has a 270 Ohm serial resistor. The same configuration with 47 Ohm resistor works on my DE1 Board.
I tried the User0 on Spare IO with 47 OHM resistor but still no loading.
What are the differences between Spartan 3 and Cyclone 2 IO ports ? Do i need a simple transistor amplifier ?