// nandgame counter

`timescale 1us/1us

`ifndef NANDGAME_COUNTER
`define NANDGAME_COUNTER

module  counter #(
  parameter DATA_WIDTH = 16
) (
  // input / value to store in counter
  input [(DATA_WIDTH-1):0] X_in,
  // whether to store input (else increment)
  input wire st_store_X_in,
  // clock
  input wire clk_in,

  // counter value
  output wire [(DATA_WIDTH-1):0] counter_out
);


/*
A counter component increments a 16-bit number for each clock cycle.

If st_store_X_in (store) is 1, then the input value X_in is used as the new counter value.

If st_store_X_in is 0, then the previous counter value is incremented by 1.

The counter output changes when clk_in (clock signal) changes to 0.
Input	Effect
st_store_X_in	clk_in	
0	0	set next to output + 1
1	0	set next to X_in

output is the current output of the component. next becomes the current output when clk_in changes to 0.
*/

reg [(DATA_WIDTH-1):0] counter_int;

initial begin
  counter_int = 0;
end

always @(negedge clk_in) begin
  if (st_store_X_in)
    counter_int <= X_in;
  else
    counter_int <= counter_int + 1;
end

assign counter_out = counter_int;

endmodule

`endif