mirror of
https://github.com/sehugg/8bitworkshop.git
synced 2024-12-29 11:31:42 +00:00
71 lines
2.2 KiB
Verilog
71 lines
2.2 KiB
Verilog
|
|
`ifndef HVSYNC_GENERATOR_H
|
|
`define HVSYNC_GENERATOR_H
|
|
|
|
/*
|
|
Video sync generator, used to drive a VGA monitor.
|
|
Timing from: https://en.wikipedia.org/wiki/Video_Graphics_Array
|
|
To use:
|
|
- Wire the hsync and vsync signals to top level outputs
|
|
- Add a 3-bit (or more) "rgb" output to the top level
|
|
*/
|
|
|
|
module hvsync_generator(clk, reset, hsync, vsync, display_on, hpos, vpos);
|
|
|
|
input clk;
|
|
input reset;
|
|
output reg hsync, vsync;
|
|
output display_on;
|
|
output reg [9:0] hpos;
|
|
output reg [9:0] vpos;
|
|
|
|
// declarations for TV-simulator sync parameters
|
|
// horizontal constants
|
|
parameter H_DISPLAY = 640; // horizontal display width
|
|
parameter H_BACK = 48; // horizontal left border (back porch)
|
|
parameter H_FRONT = 16; // horizontal right border (front porch)
|
|
parameter H_SYNC = 96; // horizontal sync width
|
|
// vertical constants
|
|
parameter V_DISPLAY = 480; // vertical display height
|
|
parameter V_TOP = 33; // vertical top border
|
|
parameter V_BOTTOM = 10; // vertical bottom border
|
|
parameter V_SYNC = 2; // vertical sync # lines
|
|
// derived constants
|
|
parameter H_SYNC_START = H_DISPLAY + H_FRONT;
|
|
parameter H_SYNC_END = H_DISPLAY + H_FRONT + H_SYNC - 1;
|
|
parameter H_MAX = H_DISPLAY + H_BACK + H_FRONT + H_SYNC - 1;
|
|
parameter V_SYNC_START = V_DISPLAY + V_BOTTOM;
|
|
parameter V_SYNC_END = V_DISPLAY + V_BOTTOM + V_SYNC - 1;
|
|
parameter V_MAX = V_DISPLAY + V_TOP + V_BOTTOM + V_SYNC - 1;
|
|
|
|
wire hmaxxed = (hpos == H_MAX) || reset; // set when hpos is maximum
|
|
wire vmaxxed = (vpos == V_MAX) || reset; // set when vpos is maximum
|
|
|
|
// horizontal position counter
|
|
always @(posedge clk)
|
|
begin
|
|
hsync <= (hpos>=H_SYNC_START && hpos<=H_SYNC_END);
|
|
if(hmaxxed)
|
|
hpos <= 0;
|
|
else
|
|
hpos <= hpos + 1;
|
|
end
|
|
|
|
// vertical position counter
|
|
always @(posedge clk)
|
|
begin
|
|
vsync <= (vpos>=V_SYNC_START && vpos<=V_SYNC_END);
|
|
if(hmaxxed)
|
|
if (vmaxxed)
|
|
vpos <= 0;
|
|
else
|
|
vpos <= vpos + 1;
|
|
end
|
|
|
|
// display_on is set when beam is in "safe" visible frame
|
|
assign display_on = (hpos<H_DISPLAY) && (vpos<V_DISPLAY);
|
|
|
|
endmodule
|
|
|
|
`endif
|