psx_timer.v

`default_nettype none

module psx_timer #(parameter WIDTH = 16)
   (input                    clk,
    input 		     aresetn,
    input [WIDTH - 1:0]      target,
    input 		     reset_on_target,
    input 		     irq_on_target,
    input 		     irq_ack,
    input [WIDTH - 1:0]      counter_value,
    input 		     counter_w,

    output reg [WIDTH - 1:0] counter,
    output reg 		     irq);

   always @(posedge clk or negedge aresetn) begin
      if (~aresetn)
	irq <= 0;
      else begin
	 if (irq_ack)
	   irq <= 0;
	 else if (irq_on_target && counter == target)
	   irq <= 1;
	 else if (& counter)
	   irq <= 1;
	 else
	   irq <= irq;
      end
   end

   always @(posedge clk or negedge aresetn) begin
      if (~aresetn)
	counter <= 0;
      else begin
	 if (counter_w)
	   counter <= counter_value;
	 else if (reset_on_target && counter == target)
	   counter <= 0;
	 else if (& counter)
	   counter <= 0;
	 else
	   counter <= counter + 1;
      end
   end

endmodule