`define ADDR_P1 16'hFF00

/* note: buttons are 'pressed' when the input is high */

module Buttons(
	input core_clk,
	input wr,
	input rd,
	input [15:0] addr,
	inout [7:0] data,
	input [7:0] buttons,
	output reg int
	);

	reg rdlatch;
	reg [15:0] addrlatch;

	reg [7:0] p1;
	reg [3:0] oldp1013;

	assign data = (rdlatch && (addrlatch == `ADDR_P1)) ? p1 : 8'bzzzzzzzz;

	wire [3:0] p1013 = (p1[4] ? 4'b1111 : ~buttons[3:0]) & (p1[5] ? 4'b1111 : ~buttons[7:4]);

	always @ (posedge core_clk) begin
		if(wr) begin
			case(addr)
			`ADDR_P1: p1[5:4] <= data[5:4];
			endcase
		end
		rdlatch <= rd;
		addrlatch <= addr;
		p1[3:0] <= p1013;
		oldp1013 <= p1013;
		int <= | (oldp1013 & (oldp1013 ^ p1013));
	end
endmodule