[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 25

`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 + 161)) && (vgay > `YOFS) && (vgay < (`YOFS + 144))) ? {failandloss[2],failandloss[1],1'b0,failandloss[2],failandloss[1],1'b0,failandloss[0],1'b0} :
                ((vgax < 640) && (vgay < 480)) ? 8'b00000000 :
                8'b00000000;
        
        always @(posedge vgaclk)
        begin
                if (vgax >= (`XRES + `XFPORCH + `XSYNC + `XBPORCH))
                begin
                        if (vgay >= (`YRES + `YFPORCH + `YSYNC + `YBPORCH)) begin
                                vgafb <= 0;
                                vgay <= 0;
                                vgax <= 0;
                        end else begin
                                vgay <= vgay + 1;
                                vgax <= 0;
                        end
                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 + 161)) && (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