xilinx/xc7/tests/bufgce/bufgce_nexys_video.v

module top (
    input  wire clk,

    input  wire [7:0] sw,
    output wire [7:0] led,

    input  wire rx,
    output wire tx
);
    wire clk_out;
    reg [26:0] counter;

    BUFGCE buf1(.CE(sw[0]), .I(clk), .O(clk_out));

    always @(posedge clk_out) begin
        counter <= counter + 1;
    end

   assign tx = rx;
   assign led[0] = counter[25];
   assign led[1] = sw[1];
endmodule