`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Company: 
// Engineer: 
// 
// Create Date:    19:03:41 12/15/2007 
// Design Name: 
// Module Name:    NTSC 
// Project Name: 
// Target Devices: 
// Tool versions: 
// Description: 
//
// Dependencies: 
//
// Revision: 
// Revision 0.01 - File Created
// Additional Comments: 
//
//////////////////////////////////////////////////////////////////////////////////
module NTSC(signal, trigger, clk);
output reg [7:0] signal;
output reg trigger;

input clk;
////////////////////////////////
// states
////////////////////////////////
reg [1:0] lineState;
parameter	sFP = 0,
			sHSYNC = 1,
			sBP = 2,
			sLINE = 3;

reg [0:0] syncState;
parameter	sIMAGE = 0,
			sVSYNC = 1;

reg [1:0] vbiState;
parameter	sPRE = 0,
			sVERT = 1,
			sPOST = 2,
			sBLANK = 3;

reg [0:0] fieldState;
parameter	sEVEN = 0,
			sODD = 1;

initial begin
	lineState = sFP;
	syncState = sIMAGE;
	fieldState = sEVEN;
end


////////////////////////////////
// signal
////////////////////////////////
parameter	nBLACK = 77,
		nSYNC = 0;

reg [7:0] pixel, level;
reg [9:0] line;


////////////////////////////////
// timers
////////////////////////////////
// timer counts must be 1 less than calculated because timer starts at 0!!!
// clkFreq = 25000000;
reg [31:0] lineTimer;

reg [63:0] posTimer;
reg [6:0] xpos;
reg [7:0] ypos;
reg [6:0] xpos2;
reg [7:0] ypos2;
reg [3:0] xvel;
reg [3:0] yvel;
reg [3:0] xvel2;
reg [3:0] yvel2;
reg odd;

reg resetTimer;

initial begin
	lineTimer = 0;
	resetTimer = 0;
	xpos = 12;
	ypos = 68;
	xvel = 7;//0-10; 5 is no velocity
	yvel = 6;//0-10; 5 is no velocity
	xpos2 = 112;
	ypos2 = 38;
	xvel2 = 3;//0-10; 5 is no velocity
	yvel = 8;//0-10; 5 is no velocity
end


////////////////////////////////
// the thing
////////////////////////////////
always @(posedge posTimer[20]) begin
if (odd) begin
	xpos = xpos+(xvel-5);//0-127
	ypos = ypos+2*(yvel-5);//0-255
	if (((xpos+(xvel-5))>125)|((xpos+(xvel-5))<2)) begin
		case (xvel)
		0: xvel=10;
		1: xvel=9;
		2: xvel=8;
		3: xvel=7;
		4: xvel=6;
		6: xvel=4;
		7: xvel=3;
		8: xvel=2;
		9: xvel=1;
		10: xvel=0;
		endcase
		end
	if (((ypos+2*(yvel-5))>252)|((ypos+2*(yvel-5))<4)) begin
		case (yvel)
		0: yvel=10;
		1: yvel=9;
		2: yvel=8;
		3: yvel=7;
		4: yvel=6;
		6: yvel=4;
		7: yvel=3;
		8: yvel=2;
		9: yvel=1;
		10: yvel=0;
		endcase
		end
	xpos2 = xpos2+(xvel2-5);//0-127
	ypos2 = ypos2+2*(yvel2-5);//0-255
	if (((xpos2+(xvel2-5))>127)|((xpos2+(xvel2-5))<2)) begin //(((xpos+xvel-xpos2-xvel2)<2)&&((xpos+xvel-xpos2-xvel2)>2)) thids is a thought... forget it
		case (xvel2)
		0: xvel2=10;
		1: xvel2=9;
		2: xvel2=8;
		3: xvel2=7;
		4: xvel2=6;
		6: xvel2=4;
		7: xvel2=3;
		8: xvel2=2;
		9: xvel2=1;
		10: xvel2=0;
		endcase
		end
	if (((ypos2+2*(yvel2-5))>256)|((ypos2+2*(yvel2-5))<4)) begin
		case (yvel2)
		0: yvel2=10;
		1: yvel2=9;
		2: yvel2=8;
		3: yvel2=7;
		4: yvel2=6;
		6: yvel2=4;
		7: yvel2=3;
		8: yvel2=2;
		9: yvel2=1;
		10: yvel2=0;
		endcase
		end
	end
	end

always @(posedge clk) begin
	if (resetTimer) begin
		lineTimer = 0;
		resetTimer = 0;
		odd=odd+1;
	end else begin
		lineTimer = lineTimer + 1;
	end
	
	posTimer = posTimer + 1;
	
	case (syncState)
	
	//////////////////////////////
	// image
	//////////////////////////////
	
	sIMAGE: begin
	trigger = 0;
	
		case (lineState)
		sFP: begin
			signal = nBLACK;
			if (lineTimer >= 34) begin	// 1.4 us
				lineState = sHSYNC;
				resetTimer = 1;
			end
		end
		sHSYNC: begin
			signal = nSYNC;
			if (lineTimer >= 117) begin	// 4.7 us
				lineState = sBP;
				resetTimer = 1;
				
				// set up the pixel address
				pixel = 0;
//				address = line * 256 + pixel;
			end
		end
		sBP: begin
			signal = nBLACK;
			if (lineTimer >= 146) begin	// 5.9 us
				lineState = sLINE;
				resetTimer = 1;
			end
		end
		sLINE: begin
			if (pixel < 255) begin
				signal = level;
				if (lineTimer >= 4) begin	// 200 ns per pixel
					if (pixel<48||pixel>128+48||line<128||line>128+256) begin
						level = 128;
						end else begin
						if (line<128+ypos-4||line>128+ypos+4||pixel<48+xpos-2||pixel>48+xpos+2) begin //make square at pos.
							if (line<128+ypos2-2||line>128+ypos2+2||pixel<48+xpos2-1||pixel>48+xpos2+1) begin
								level = 255;
								end else begin
								level = 128;
							end
							end else begin
							level = nBLACK;
						end
					end
					
					pixel = pixel + 1;
					
					resetTimer = 1;
				end
			end else begin
				line = line + 2;
				lineState = sFP;
				
				if (line >= 483) begin
					syncState = sVSYNC;
					vbiState = sPRE;
					line = 0;
					resetTimer = 1;
				end
			end
	
		end
		endcase
	end
	
	//////////////////////////////
	// vertical synchronization
	//////////////////////////////
	sVSYNC: begin
if (fieldState == sEVEN) begin
	trigger = 1;
end

	
		case (vbiState)
		sPRE: begin
			case (lineState)
			sFP: begin
				signal = nSYNC;
				if (lineTimer >= 34) begin	// 1.4 us
					lineState = sLINE;
					resetTimer = 1;
				end
			end
			sLINE: begin
				signal = nBLACK;
				if (lineTimer >= 758) begin	// 63.5/2 - 1.4 us
					lineState = sFP;
					resetTimer = 1;
					line = line + 1;
					
					if ((fieldState == sEVEN && line >= 7) || (fieldState == sODD && line >= 6)) begin
						vbiState = sVERT;
						line = 0;
					end
				end
			end
			endcase
		end
		sVERT: begin
			case (lineState)
			sFP: begin
				signal = nSYNC;
				if (lineTimer >= 675) begin	// 63.5/2 - 4.7 us
					lineState = sHSYNC;
					resetTimer = 1;
				end
			end
			sHSYNC: begin
				signal = nBLACK;
				if (lineTimer >= 117) begin	// 4.7 us
					lineState = sFP;
					resetTimer = 1;
					line = line + 1;
					
					if (line >= 6) begin
						vbiState = sPOST;
						line = 0;
					end
				end
			end
			endcase
		end
		sPOST: begin
			case (lineState)
			sFP: begin
				signal = nSYNC;
				if (lineTimer >= 34) begin	// 1.4 us
					lineState = sLINE;
					resetTimer = 1;
				end
			end
			sLINE: begin
				signal = nBLACK;
				if (lineTimer >= 758) begin	// 63.5/2 - 1.4 us
					lineState = sFP;
					resetTimer = 1;
					line = line + 1;
					
					if ((fieldState == sEVEN && line >= 5) || (fieldState == sODD && line >= 6)) begin
						vbiState = sBLANK;
						line = 0;
					end
				end
			end
			endcase
		end
		sBLANK: begin
			case (lineState)
			sFP: begin
				signal = nSYNC;
				if (lineTimer >= 117) begin		// 4.7 us
					lineState = sLINE;
					resetTimer = 1;
				end
			end
			sLINE: begin
				signal = nBLACK;
				if (lineTimer >= 1469) begin	// 63.5 - 4.7 us
					lineState = sFP;
					resetTimer = 1;
					line = line + 1;
					
					if ((fieldState == sEVEN && line >= 12) || (fieldState == sODD && line >= 11)) begin
						lineState = sFP;
						syncState = sIMAGE;
						fieldState = !fieldState;
						
						// start on line 0 if sODD, line 1 if sEVEN
						line = fieldState;
					end
				end
			end
			endcase
		end
		endcase
	end
	endcase
end


endmodule