// LASER310 VZ200
// mc6847

module MC6847_VGA(
PIX_CLK,
RESET_N,

RD,
DD,
DA,

AG,
AS,
EXT,
INV,
GM,
CSS,

// vga
blank,
VGA_OUT_HSYNC,
VGA_OUT_VSYNC,
VGA_OUT_RED,
VGA_OUT_GREEN,
VGA_OUT_BLUE
);

input			PIX_CLK;
input			RESET_N;

output	wire			RD;
output	wire	[12:0]	DA;		// 8KB
input			[7:0]	DD;
input					AG;
input					AS;
input					EXT;
input					INV;
input					CSS;
input			[2:0]	GM;
output	wire			blank;
output	wire			VGA_OUT_HSYNC;
output	wire			VGA_OUT_VSYNC;
output	wire	[7:0]	VGA_OUT_RED;
output	wire	[7:0]	VGA_OUT_GREEN;
output	wire	[7:0]	VGA_OUT_BLUE;


reg				LATCHED_AG;
reg				LATCHED_AS;
reg				LATCHED_EXT;
reg				LATCHED_INV;
reg		[2:0]	LATCHED_GM;
reg				LATCHED_CSS;

wire			pixel_clock;				// generated from SYSTEM CLOCK
wire			reset;						// reset asserted when DCMs are NOT LOCKED

wire	[7:0]	vga_red;				// red video data
wire	[7:0]	vga_green;				// green video data
wire	[7:0]	vga_blue;				// blue video data

// internal video timing signals
wire 			h_synch;					// horizontal synch for VGA connector
wire 			v_synch;					// vertical synch for VGA connector
//wire 			blank;						// composite blanking
wire	[10:0]	pixel_count;				// bit mapped pixel position within the line
wire	[9:0]	line_count;					// bit mapped line number in a frame lines within the frame

wire			show_border;

// text
wire	[3:0]	subchar_pixel;				// pixel position within the character
wire	[4:0]	subchar_line;				// identifies the line number within a character block
wire	[6:0]	char_column;				// character number on the current line
wire	[6:0]	char_line;					// line number on the screen

// graph
wire	[8:0]	graph_pixel;				// pixel number on the current line
wire	[9:0]	graph_line_2x;				// line number on the screen
wire	[9:0]	graph_line_3x;				// line number on the screen

/*
wire	[11:0]	ROM_ADDRESS;
wire	[7:0]	ROM_DATA;
*/

assign	reset = ~RESET_N;
assign	pixel_clock = PIX_CLK;

//assign	vga_red = 8'hff;
//assign	vga_green = 8'h7f;
//assign	vga_blue = 8'h7f;

// Character generator
/*
char_rom_4k_altera char_rom(
	.address(ROM_ADDRESS),
	.clock(pixel_clock),
	.q(ROM_DATA)
);
*/

// 为了防止闪屏，再垂直回扫信号产生时，锁存模式信号。

always @ (posedge v_synch or negedge RESET_N)
begin
	if(!RESET_N)
	begin
		LATCHED_AG		<=	1'b0;
		LATCHED_AS		<=	1'b0;
		LATCHED_EXT		<=	1'b0;
		LATCHED_INV		<=	1'b0;
		LATCHED_GM		<=	3'b0;
		LATCHED_CSS		<=	1'b0;
	end
	else
	begin
		LATCHED_AG <= AG;
		LATCHED_AS <= AS;
		LATCHED_EXT <= EXT;
		LATCHED_INV <= INV;
		LATCHED_GM <= GM;
		LATCHED_CSS <= CSS;
	end
end

// instantiate the character generator
PIXEL_DISPLAY PIXEL_DISPLAY(
	.pixel_clock(pixel_clock),
	.reset(reset),
	.show_border(show_border),
	// mode
	.ag(LATCHED_AG),
	.gm(LATCHED_GM),
	.css(LATCHED_CSS),
	// text
	.char_column(char_column),
	.char_line(char_line),
	.subchar_line(subchar_line),
	.subchar_pixel(subchar_pixel),
	// graph
	.graph_pixel(graph_pixel),
	.graph_line_2x(graph_line_2x),
	.graph_line_3x(graph_line_3x),
	// vram
	.vram_rd_enable(RD),
	.vram_addr(DA),
	.vram_data(DD),
	// vga
	.vga_red(vga_red),
	.vga_green(vga_green),
	.vga_blue(vga_blue)
);

// instantiate the video timing generator
SVGA_TIMING_GENERATION SVGA_TIMING_GENERATION
(
	pixel_clock,
	reset,
	h_synch,
	v_synch,
	blank,
	pixel_count,
	line_count,

	show_border,

	// text
	subchar_pixel,
	subchar_line,
	char_column,
	char_line,

	// graph
	graph_pixel,
	graph_line_2x,
	graph_line_3x
);

// instantiate the video output mux
VIDEO_OUT VIDEO_OUT
(
	pixel_clock,
	reset,
	vga_red,
	vga_green,
	vga_blue,
	h_synch,
	v_synch,
	blank,

	VGA_OUT_HSYNC,
	VGA_OUT_VSYNC,
	VGA_OUT_RED,
	VGA_OUT_GREEN,
	VGA_OUT_BLUE
);

endmodule