diff --git a/lib/CPUs/MIPS/src/core/mips_shifter.vhd b/lib/CPUs/MIPS/src/core/mips_shifter.vhd
index cff2c7d..34036a2 100644
--- a/lib/CPUs/MIPS/src/core/mips_shifter.vhd
+++ b/lib/CPUs/MIPS/src/core/mips_shifter.vhd
@@ -49,7 +49,21 @@ architecture Behavioral of shifter is
 	signal sa_rnd			: unsigned (4 downto 0);
 	signal fill	: std_logic;
 	
+	type fill_mask_rom_t is array (0 to 2*data_width-1) of unsigned(data_width-1 downto 0);
 --------------------------------------------------------------------------
+function gen_fill_mask_rom(data_width : natural) return fill_mask_rom_t is
+	variable result : fill_mask_rom_t;
+	begin
+		for i in 0 to data_width-1 loop
+			result(i) := (data_width-1-i downto 0 => '0') & (i-1 downto 0 => '1');
+		end loop;	
+		for i in 0 to data_width-1 loop
+			result(data_width+i) := (i-1 downto 0 => '1') & (data_width-1-i downto 0 => '0');
+		end loop;	
+	return result;
+	
+end gen_fill_mask_rom;
+
 function rot_stage(x : unsigned; en : std_logic; stage_num : natural) return unsigned is
 	variable result : unsigned(x'range);
 	constant sa : natural := 2**stage_num;
@@ -63,52 +77,39 @@ function rot_stage(x : unsigned; en : std_logic; stage_num : natural) return uns
 	
 end rot_stage;
 
-function rot_fill(x : unsigned; fill : std_logic; shift_right : std_logic; sa : natural) return unsigned is
-	variable result : unsigned(x'range) := (others => '0');
-	variable j : integer;
-	begin
-		
-	if shift_right = '0' then
-		for i in 0 to x'left loop
-			if i >= sa then
-				result(i) := x(i);
-			else
-				result(i) := fill;
-			end if;	
-		end loop;
-	else	
-		j := x'left;
-		for i in 0 to x'left loop
-			if i < sa then
-				result(j) := fill;
-			else
-				result(j) := x(j);
-			end if;	
-			j := j - 1;
-		end loop;
-	end if;	
-	return result;
+	constant fill_mask_rom	: fill_mask_rom_t := gen_fill_mask_rom(data_width);
+	signal fill_mask		: unsigned(data_width-1 downto 0);
+	signal fill_mask_addr	: unsigned(5 downto 0);
+	signal dout_filled		: unsigned (data_width-1 downto 0);
 	
-end rot_fill;
-
 --------------------------------------------------------------------------
 begin
 
-	rot_data(0)	<= din;
-
+	rot_data(0)		<= din;
+	
 gen_rotate_right:
 	for stage in 0 to 4 generate
 	begin
 		rot_data(stage+1) <= rot_stage(rot_data(stage), sa_rnd(stage), stage);
 	end generate;
 	
-	sa_rnd	<= shift_ctrl.shamt_rnd;
-	fill	<= shift_ctrl.shift_arith and din(data_width-1);
-	dout	<= rot_fill(rot_data(5), fill, shift_ctrl.shift_right, to_integer(shift_ctrl.shamt_nrm)) after 5 ns;
---	dout	<= rot_data(5);
-	
-	
+	sa_rnd			<= shift_ctrl.shamt_rnd;
+	fill			<= shift_ctrl.shift_arith and din(data_width-1);
+	fill_mask_addr	<= shift_ctrl.shift_right & shift_ctrl.shamt_nrm;
+	fill_mask		<= fill_mask_rom(to_integer(fill_mask_addr));
 
+proc_fill_neu:
+	process(fill_mask, fill, rot_data(5))
+	begin
+		if fill = '1' then
+			dout_filled	<= rot_data(5) or fill_mask;
+		else	
+			dout_filled	<= rot_data(5) and not fill_mask;
+		end if;
+	end process;
+	
+	dout	<= dout_filled after 5 ns;
+	
 --------------------------------------------------------------------------
 end Behavioral;