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8bitworkshop/presets/verilog/ball_slip_counter.v

110 lines
2.9 KiB
Verilog

`include "hvsync_generator.v"
module ball_slip_counter_top(clk, reset, hsync, vsync, rgb);
input clk;
input reset;
output hsync, vsync;
output [2:0] rgb;
wire display_on;
wire [8:0] hpos;
wire [8:0] vpos;
// 9-bit ball timers
reg [8:0] ball_htimer;
reg [8:0] ball_vtimer;
// 4-bit motion codes
reg [3:0] ball_horiz_move;
reg [3:0] ball_vert_move;
// 4-bit stop codes
localparam ball_horiz_stop = 4'd11;
localparam ball_vert_stop = 4'd10;
// 5-bit constants to load into counters
localparam ball_horiz_prefix = 5'b01100; // 192
localparam ball_vert_prefix = 5'b01111; // 240
// reset ball; will be unset when video beam reaches center position
reg ball_reset;
// video sync generator
hvsync_generator hvsync_gen(
.clk(clk),
.reset(reset),
.hsync(hsync),
.vsync(vsync),
.display_on(display_on),
.hpos(hpos),
.vpos(vpos)
);
// update horizontal timer
always @(posedge clk or posedge ball_reset)
begin
if (ball_reset || &ball_htimer) begin
if (ball_reset || &ball_vtimer) // nudge ball in horiz. dir
ball_htimer <= {ball_horiz_prefix, ball_horiz_move};
else // reset timer but don't move ball horizontally
ball_htimer <= {ball_horiz_prefix, ball_horiz_stop};
end else
ball_htimer <= ball_htimer + 1;
end
// update vertical timer
always @(posedge hsync or posedge ball_reset)
begin
if (ball_reset || &ball_vtimer) // reset timer
ball_vtimer <= {ball_vert_prefix, ball_vert_move};
else
ball_vtimer <= ball_vtimer + 1;
end
// reset ball position
always @(posedge clk or posedge reset)
begin
if (reset)
ball_reset <= 1;
else if (hpos == 128 && vpos == 128)
ball_reset <= 0; // un-reset when beam reaches center position
end
// collide with vertical and horizontal boundaries?
wire ball_vert_collide = ball_vgfx && vpos >= 240;
wire ball_horiz_collide = ball_hgfx && hpos >= 256 && vpos == 255;
// vertical bounce
always @(posedge ball_vert_collide or posedge reset)
begin
if (reset)
ball_vert_move <= 4'd9; // initial vertical velocity
else
ball_vert_move <= (4'd9 ^ 4'd11) ^ ball_vert_move; // change dir.
end
// horizontal bounce
always @(posedge ball_horiz_collide or posedge reset)
begin
if (reset)
ball_horiz_move <= 4'd10; // initial horizontal velocity
else
ball_horiz_move <= (4'd10 ^ 4'd12) ^ ball_horiz_move; // change dir.
end
// compute ball display
wire ball_hgfx = ball_htimer >= 508; // 512-508 = 4 pixel ball
wire ball_vgfx = ball_vtimer >= 508;
wire ball_gfx = ball_hgfx && ball_vgfx;
// compute grid display
wire grid_gfx = (((hpos&7)==0) && ((vpos&7)==0));
// combine into RGB signals
wire r = display_on && (ball_hgfx | ball_gfx);
wire g = display_on && (grid_gfx | ball_gfx);
wire b = display_on && (ball_vgfx | ball_gfx);
assign rgb = {b,g,r};
endmodule