User manual

Blinking an LED
// File name: Blinky.sv
//
// 10Sep2013 .. initial version .. K.Metzger
//
module Blinky // top level module for this example
(
output LEDR[0], // signal names must match those in .qsf file
input CLOCK_50
);
logic led_bit, clk;
logic [24:0] counter; // sized to generate 0.5 second event
initial begin // initialize the start-up
led_bit = 0;
counter = 25000000-1; // count for 1/2 second at 50 MHz
end
assign clk = CLOCK_50; // connect 50 MHz clock to generic clk
assign LEDR[0] = led_bit; // connect the led_bit to RED LED 0
always_ff @(posedge clk) begin // use rising edge of the clock
counter <= counter-1; // set next counter value to current minus 1
if (counter == 0) begin // but if the counter equals 0
led_bit <= ~led_bit; // complement the led bit
counter <= 25000000-1; // reset the counter
end
end
endmodule
EECS 452 – Fall 2014 Lecture 5 – Page 97/143 Tuesday – September 16, 2014