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library ieee;
use ieee.std_logic_1164.all;
use work.ppu_consts.all;
entity ppu_comp is port (
OE : in std_logic; -- global output enable (screen active)
FG_HIT : in std_logic_vector(PPU_FG_SPRITE_COUNT-1 downto 0); -- foreground hit array
BG_EN : out std_logic; -- background enable output
FG_EN : out std_logic_vector(PPU_FG_SPRITE_COUNT-1 downto 0)); -- foreground enable output
end ppu_comp;
architecture Behavioral of ppu_comp is
signal FG_HIT_EMPTY : std_logic_vector(PPU_FG_SPRITE_COUNT-1 downto 0) := (others => '0');
signal TMP_BG_EN : std_logic; -- background enable output
signal TMP_FG_EN : std_logic_vector(PPU_FG_SPRITE_COUNT-1 downto 0); -- foreground enable output
begin
BG_EN <= TMP_BG_EN and OE;
FG_EN <= TMP_FG_EN and OE;
process (FG_HIT)
variable HIT : boolean := false;
begin
-- check if FG_HIT is not empty
if FG_HIT /= FG_HIT_EMPTY then
TMP_BG_EN <= '0';
for i in 0 to PPU_FG_SPRITE_COUNT-1 loop
-- if FG_HIT is the first one then enable it
if(FG_HIT(i) = '1' and HIT = false) then
TMP_FG_EN(i) <= '1';
HIT := true;
else
-- make rest low
TMP_FG_EN(i) <= '0';
end if;
end loop;
HIT := false;
else
TMP_BG_EN <= '1';
TMP_FG_EN <= (others => '0');
end if;
end process;
end Behavioral;
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