nand2/05_Computer_Architecture/Clock25_Reset20.v

/**
* Uses CLK of 100MHz to generate:
* internal clock signal clk with 25MHz and
* a reset signal of approx. 20us length
*/
`default_nettype none
module Clock25_Reset20(
    input CLK,              // external clock 100 MHz
    output reg clk,         // internal clock 25 Mhz
    output reg reset        // reset signal approx. 20us
);

    // Put your code here:
    reg boot=1;
    reg [3:0]  ccount=0;
    reg [12:0] rcount=0;

    always @(posedge CLK) begin
        if (boot == 1) begin
            boot <= (rcount == 4095) ? 0 : 1;
            rcount <= (rcount == 4095) ? 0 : rcount + 1;
            reset <= (rcount >= 2048) ? 0 : 1;
        end
        ccount <= (ccount == 3) ? 0 : ccount + 1;
        clk <= (ccount >= 2) ? 1 : 0;
    end
endmodule