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`default_nettype none
`timescale 1ns/1ns
`include "messages.vh"
`ifndef SIMULATION
`error_SIMULATION_not_defined
; /* Cause syntax error */
`endif
module VGA_640_480_60Hz(
input wire horizontal_sync,
input wire vertical_sync,
input wire [2:0] red,
input wire [2:0] green,
input wire [2:0] blue,
output reg [9:0] image_writes
);
initial
image_writes <= 0;
parameter FRONT_PORCH = 0;
parameter SYNC_PULSE = 1;
parameter BACK_PORCH = 2;
parameter ACTIVE_VIDEO = 3;
parameter UNKNOWN_STATE = 4;
integer h_state;
integer v_state;
initial begin
h_state <= UNKNOWN_STATE;
v_state <= UNKNOWN_STATE;
end
parameter H_SYNC_POLARITY = 1'b0;
parameter H_FRONT_PORCH_LENGTH = 16;
parameter H_SYNC_PULSE_LENGTH = 96;
parameter H_BACK_PORCH_LENGTH = 48;
parameter H_ACTIVE_VIDEO_LENGTH = 640;
parameter V_SYNC_POLARITY = 1'b1;
parameter V_FRONT_PORCH_LENGTH = 10;
parameter V_SYNC_PULSE_LENGTH = 2;
parameter V_BACK_PORCH_LENGTH = 33;
parameter V_ACTIVE_VIDEO_LENGTH = 480;
reg [8:0] picture
[V_ACTIVE_VIDEO_LENGTH - 1 : 0]
[H_ACTIVE_VIDEO_LENGTH - 1 : 0];
integer h_counter, v_counter;
reg error;
wire unexpected_h_sync_pulse;
wire missing_h_sync_pulse;
assign unexpected_h_sync_pulse = horizontal_sync == H_SYNC_POLARITY &&
h_state != SYNC_PULSE;
assign missing_h_sync_pulse = horizontal_sync != H_SYNC_POLARITY &&
h_state == SYNC_PULSE;
wire unexpected_v_sync_pulse;
wire missing_v_sync_pulse;
assign unexpected_v_sync_pulse = vertical_sync == V_SYNC_POLARITY &&
v_state != SYNC_PULSE;
assign missing_v_sync_pulse = vertical_sync != V_SYNC_POLARITY &&
v_state == SYNC_PULSE;
wire new_line;
assign new_line = h_state == BACK_PORCH &&
h_counter + 1 == H_BACK_PORCH_LENGTH;
wire new_screen;
assign new_screen = v_state == BACK_PORCH &&
v_counter + 1 == V_BACK_PORCH_LENGTH && new_line;
always #40 begin
/* First, horizontal stuff */
if (unexpected_h_sync_pulse) begin
h_state <= SYNC_PULSE;
h_counter <= 1;
if (h_state != UNKNOWN_STATE) begin
`MSG(({"VGA: error: unexpected horizontal sync pulse signal ",
"(tick %0d; state %0d)"}, h_counter, h_state));
end
end else if (missing_h_sync_pulse) begin
h_state <= BACK_PORCH;
h_counter <= 1;
`MSG(({"VGA: error: missing expected horizontal sync pulse signal ",
"(tick %0d of sync pulse)"}, h_counter));
end else begin
case (h_state)
FRONT_PORCH : begin
if (h_counter + 1 != H_FRONT_PORCH_LENGTH) begin
h_counter <= h_counter + 1;
end else begin
h_state <= SYNC_PULSE;
h_counter <= 0;
end
end
SYNC_PULSE : begin
if (h_counter + 1 != H_SYNC_PULSE_LENGTH) begin
h_counter <= h_counter + 1;
end else begin
h_state <= BACK_PORCH;
h_counter <= 0;
end
end
BACK_PORCH : begin
if (h_counter + 1 != H_BACK_PORCH_LENGTH) begin
h_counter <= h_counter + 1;
end else begin
h_state <= ACTIVE_VIDEO;
h_counter <= 0;
end
end
ACTIVE_VIDEO : begin
if (v_state == ACTIVE_VIDEO) begin
picture[v_counter][h_counter] <= {red, green, blue};
end
if (h_counter + 1 != H_ACTIVE_VIDEO_LENGTH) begin
h_counter <= h_counter + 1;
end else begin
h_state <= FRONT_PORCH;
h_counter <= 0;
end
end // case: ACTIVE_VIDEO
endcase // case (h_state)
end // else: !if(missing_h_sync_pulse)
/* Vertical stuff is similar to horizontal */
if (h_state == ACTIVE_VIDEO) begin
if (unexpected_v_sync_pulse) begin
v_state <= SYNC_PULSE;
v_counter <= 0;
if (v_state != UNKNOWN_STATE) begin
`MSG(({"VGA: error: unexpected vertical sync pulse signal ",
"(line %0d; state %0d)"}, v_counter, v_state));
end
end else if (missing_v_sync_pulse) begin
v_state <= BACK_PORCH;
v_counter <= 0;
`MSG(({"VGA: error: missing expected vertical sync pulse signal ",
"(line %0d of sync pulse)"}, v_counter));
end
end // if (h_state == ACTIVE_VIDEO)
if (new_line) begin
case (v_state)
FRONT_PORCH : begin
if (v_counter + 1 != V_FRONT_PORCH_LENGTH) begin
v_counter <= v_counter + 1;
end else begin
v_state <= SYNC_PULSE;
v_counter <= 0;
end
end
SYNC_PULSE : begin
if (v_counter + 1 != V_SYNC_PULSE_LENGTH) begin
v_counter <= v_counter + 1;
end else begin
v_state <= BACK_PORCH;
v_counter <= 0;
end
end
BACK_PORCH : begin
if (v_counter + 1 != V_BACK_PORCH_LENGTH) begin
v_counter <= v_counter + 1;
end else begin
v_state <= ACTIVE_VIDEO;
v_counter <= 0;
end
end
ACTIVE_VIDEO : begin
if (v_counter + 1 != V_ACTIVE_VIDEO_LENGTH) begin
v_counter <= v_counter + 1;
end else begin
v_state <= FRONT_PORCH;
v_counter <= 0;
if (!error) begin
$writememb("VGAdump.mem", picture);
`DBG(("VGA: written VGAdump.mem"));
image_writes <= image_writes + 1;
end
end // else: !if(v_counter + 1 != V_ACTIVE_VIDEO_LENGTH)
end // case: ACTIVE_VIDEO
endcase // case (v_state)
end // if (new_line)
if (unexpected_h_sync_pulse || unexpected_h_sync_pulse ||
((unexpected_v_sync_pulse || missing_v_sync_pulse) && new_line))
error <= 1;
else if (new_screen)
error <= 0;
end // always #40
endmodule // VGA_640_480_60Hz
|
