mirror of
https://github.com/Gehstock/Mist_FPGA.git
synced 2026-02-25 08:09:51 +00:00
108 lines
2.6 KiB
Systemverilog
108 lines
2.6 KiB
Systemverilog
//
|
|
// sprite.v
|
|
//
|
|
// Gameboy for the MIST board https://github.com/mist-devel
|
|
//
|
|
// Copyright (c) 2015 Till Harbaum <till@harbaum.org>
|
|
//
|
|
// This source file is free software: you can redistribute it and/or modify
|
|
// it under the terms of the GNU General Public License as published
|
|
// by the Free Software Foundation, either version 3 of the License, or
|
|
// (at your option) any later version.
|
|
//
|
|
// This source file is distributed in the hope that it will be useful,
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
// GNU General Public License for more details.
|
|
//
|
|
// You should have received a copy of the GNU General Public License
|
|
// along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
//
|
|
|
|
module sprite (
|
|
input clk,
|
|
input size16,
|
|
|
|
input [7:0] v_cnt,
|
|
input [7:0] h_cnt,
|
|
|
|
output [7:0] x,
|
|
|
|
// interface to read pixel data from memory
|
|
output [10:0] addr,
|
|
input [1:0] ds,
|
|
input [7:0] data,
|
|
|
|
output pixel_active,
|
|
output pixel_cmap,
|
|
output pixel_prio,
|
|
output [1:0] pixel_data,
|
|
|
|
input oam_wr,
|
|
input [1:0] oam_addr,
|
|
input [7:0] oam_di,
|
|
output [7:0] oam_do
|
|
);
|
|
|
|
// x position for priority detection. Invisible sprites are far to the right and
|
|
// have minimum priority
|
|
assign x = v_visible?x_pos:8'hff;
|
|
|
|
// register used to store pixel data for current line
|
|
reg [7:0] data0;
|
|
reg [7:0] data1;
|
|
|
|
always @(posedge clk) begin
|
|
if(ds[0]) data0 <= data;
|
|
if(ds[1]) data1 <= data;
|
|
end
|
|
|
|
wire [7:0] height = size16?8'd16:8'd8;
|
|
|
|
wire v_visible = (v_cnt + 8'd16 >= y_pos) && (v_cnt + 8'd16 < y_pos + height);
|
|
wire visible = v_visible && (h_cnt + 8'd8 >= x_pos) && (h_cnt < x_pos);
|
|
|
|
// x position within sprite, mirror horizontally if required
|
|
wire [2:0] col_n = h_cnt - x_pos;
|
|
wire [2:0] col = flags[1]?col_n:~col_n;
|
|
|
|
assign pixel_data = { data1[col], data0[col] };
|
|
assign pixel_active = (pixel_data != 0) && visible;
|
|
|
|
// y position within sprite, mirror vertically if required
|
|
wire [3:0] row_n = v_cnt - y_pos;
|
|
wire [3:0] row = flags[2]?~row_n:row_n;
|
|
|
|
// 16 pixel tall sprites use one more rwo counter bit and the lsb
|
|
// of the tile index is ignored
|
|
wire [10:0] addr8 = { tile , row[2:0]};
|
|
wire [10:0] addr16 = { tile[7:1] , row};
|
|
assign addr = size16?addr16:addr8;
|
|
|
|
assign pixel_cmap = flags[0];
|
|
assign pixel_prio = flags[3];
|
|
|
|
reg [7:0] y_pos;
|
|
reg [7:0] x_pos;
|
|
reg [7:0] tile;
|
|
reg [3:0] flags;
|
|
|
|
always @(posedge clk) begin
|
|
if(oam_wr) begin
|
|
case(oam_addr)
|
|
0: y_pos <= oam_di;
|
|
1: x_pos <= oam_di;
|
|
2: tile <= oam_di;
|
|
3: flags <= oam_di[7:4];
|
|
endcase
|
|
end
|
|
end
|
|
|
|
assign oam_do =
|
|
(oam_addr == 0)?y_pos:
|
|
(oam_addr == 1)?x_pos:
|
|
(oam_addr == 2)?tile:
|
|
{ flags, 4'h0 };
|
|
|
|
endmodule
|