Cut one at a framebuffer

[fpgaboy.git] / Framebuffer.v

`define XRES 640
`define XFPORCH 16
`define XSYNC 96
`define XBPORCH 48
`define YRES 480
`define YFPORCH 10
`define YSYNC 2
`define YBPORCH 29

`define XOFS ((640-160)/2)
`define YOFS ((480-144)/2)

module Framebuffer(
	input lcdclk,
	input lcdvs, lcdhs,
	input [2:0] lcdr, lcdg, input [1:0] lcdb,
	
	input vgaclk,
	output reg vgavs, vgahs,
	output wire [2:0] vgar, vgag, output wire [1:0] vgab);
	
	reg [2:0] fb [23039:0];
	
	reg [7:0] lcdx = 8'h00;
	reg [7:0] lcdy = 8'h00;
	reg [15:0] lcdfb = 16'h0000;
	
	always @(posedge lcdclk)
	begin
		/* We use BLOCKING assigns here. */
		if (lcdvs) begin
			lcdx <= 0;
			lcdy <= 0;
			lcdfb <= 0;
		end else if (lcdhs) begin
			lcdx <= 0;
			lcdy <= lcdy + 1;
		end else if (lcdx < 160) begin
			lcdx <= lcdx + 1;
			lcdfb <= lcdfb + 1;
		end
	end
	
	reg [11:0] vgax = 0, vgay = 0;
	reg [15:0] vgafb = 16'h0000;
	
	reg [2:0] failandloss;
	assign {vgar, vgag, vgab} =
		((vgax > `XOFS) && (vgax < (`XOFS + 160)) && (vgay > `YOFS) && (vgay < (`YOFS + 144))) ? {failandloss[2],2'b0,failandloss[1],2'b0,failandloss[0],1'b0} :
		((vgax < 640) && (vgay < 480)) ? 8'b11100000 :
		8'b00000000;
	
	always @(posedge vgaclk)
	begin
		if (vgax >= (`XRES + `XFPORCH + `XSYNC + `XBPORCH))
		begin
			if (vgay >= (`YRES + `YFPORCH + `YSYNC + `YBPORCH)) begin
				vgafb <= 0;
				vgay <= 0;
			end else
				vgay <= vgay + 1;
			vgax <= 0;
		end else
			vgax <= vgax + 1;
		
		vgahs <= (vgax >= (`XRES + `XFPORCH)) && (vgax < (`XRES + `XFPORCH + `XSYNC));
		vgavs <= (vgay >= (`YRES + `YFPORCH)) && (vgay < (`YRES + `YFPORCH + `YSYNC));
		
		if ((vgax > `XOFS) && (vgax < (`XOFS + 160)) && (vgay > `YOFS) && (vgay < (`YOFS + 144))) begin
			vgafb <= vgafb + 1;
			failandloss <= fb[vgafb + 1];
		end
		
		// Need thsi here; vgaclk >>> lcdclk
		if ((lcdy < 144) && (lcdx < 160))
			fb[lcdfb] <= {lcdr[2], lcdg[2], lcdb[1]};
	end
endmodule