43 lines
851 B
Verilog
43 lines
851 B
Verilog
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`include "hvsync_generator.v"
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`include "lfsr.v"
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/*
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Scrolling starfield generator using a period (2^16-1) LFSR.
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*/
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module starfield_top(clk, reset, hsync, vsync, rgb);
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input clk, reset;
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output hsync, vsync;
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output [2:0] rgb;
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wire display_on;
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wire [8:0] hpos;
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wire [8:0] vpos;
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wire [15:0] lfsr;
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hvsync_generator hvsync_gen(
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.clk(clk),
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.reset(reset),
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.hsync(hsync),
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.vsync(vsync),
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.display_on(display_on),
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.hpos(hpos),
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.vpos(vpos)
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);
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// enable LFSR only in 256x256 area
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wire star_enable = !hpos[8] & !vpos[8];
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// LFSR with period = 2^16-1 = 256*256-1
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LFSR #(16'b1000000001011,0) lfsr_gen(
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.clk(clk),
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.reset(reset),
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.enable(star_enable),
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.lfsr(lfsr));
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wire star_on = &lfsr[15:9]; // all 7 bits must be set
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assign rgb = display_on && star_on ? lfsr[2:0] : 0;
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endmodule
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