I have a Spartan3E Starter Kit, and I am trying to figure out how to use the DCM to double the freq from 50MHz to 100MHz.
I wrote a small verilog program to blink LEDs 0-3 based on the 50MHz clock, and LEDs 4-7 based on the
100MHz clock, so if it works properly, the second group of LEDs should blink twice as fast. But it doesn't work. LEDs 4-7 don't blink at all.
How do I specify (in verilog or UCF?) that the "clk_100mhz" is supposed to be the CLK2X output from the DCM? How do I specify which DCM to use, or does the compiler figure that out for itself?
Thanks for any help.
------------------------------------------------------------- // blink.v
module blink ( input wire clk_50mhz, input wire clk_100mhz, output reg[7:0] leds );
reg [20:0] cnt50; // Counter @ 50MHz reg [20:0] cnt100; // Counter @ 100MHz
initial begin cnt50