pico-ice-video/ice/mandelbrot/source/impl_1/top.sv

module top
(
	input wire clk,
	input wire dir,
	inout wire req,
	output wire fin,
	inout wire [7:0] data
);

reg dir_last;
reg req_last;

reg req_r;
reg fin_r;
reg [7:0] data_r;

reg [6:0] x;
reg [6:0] y;

reg cntr;

reg [7:0] waddr;
reg [7:0] raddr;

wire [7:0] command;

RAM command_buffer(.wclk(clk), .rclk(clk), .waddr(waddr), .raddr(raddr), .data_in(data), .write_en(dir && req), .data_out(command));

always_ff @(posedge clk) begin
	dir_last <= dir;
	req_last <= req;
	req_r <= !fin_r && !dir_last;
	
	if (dir) begin
		x <= 0;
		y <= 0;
		fin_r <= 0;
		cntr <= 0;
		raddr <= 0;
		
		if (req && req_last) begin
			waddr <= waddr + 1;
		end else begin
			waddr <= 0;
		end
	end else begin
		cntr <= !cntr;
		if (cntr) begin
			data_r <= command;
			raddr <= 1 - raddr;
			if (x + y == 0) begin
				fin_r <= 1;
			end
		end else begin
			data_r <= ((x + y) >> 1) + 16;
			
			if (x < 127) begin
				x <= x + 1;
			end else begin
				x <= 0;
				if (y < 127) begin
					y <= y + 1;
				end else begin
					y <= 0;
				end
			end
		end
	end
end

assign req = dir ? 'Z : req_r;
assign fin = fin_r;
assign data = dir ? 'Z : data_r;

endmodule