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Creato modulo CarryLookAhead

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Giulio
2019-08-29 18:08:25 +02:00
parent f4f0989ac4
commit f8ee1d5e27
13 changed files with 224 additions and 117 deletions
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58
Adder.vhd
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@@ -3,37 +3,51 @@ use IEEE.STD_LOGIC_1164.ALL;
entity Adder is
generic( BITCOUNT: integer := 8 );
port(
X, Y: in std_logic_vector((BITCOUNT-1) downto 0);
carry_in: in std_logic;
result: out std_logic_vector((BITCOUNT-1) downto 0);
carry_out: out std_logic
generic(
BITCOUNT : integer := 8
);
port(
X, Y : in std_logic_vector((BITCOUNT-1) downto 0);
CARRY_IN : in std_logic;
RESULT : out std_logic_vector((BITCOUNT-1) downto 0);
CARRY_OUT : out std_logic
);
end Adder;
architecture CarryLookAheadArch of Adder is
signal generation: std_logic_vector((BITCOUNT-1) downto 0);
signal propagation: std_logic_vector((BITCOUNT-1) downto 0);
signal carry: std_logic_vector((BITCOUNT-1) downto 0);
signal sum_no_carry: std_logic_vector((BITCOUNT-1) downto 0);
begin
generation <= X and Y;
propagation <= X or Y;
sum_no_carry <= X xor Y;
carry_look_ahead: process (generation, propagation, carry_in)
variable C: std_logic;
signal GENERATION : std_logic_vector((BITCOUNT-1) downto 0);
signal PROPAGATION : std_logic_vector((BITCOUNT-1) downto 0);
signal CARRY : std_logic_vector((BITCOUNT-1) downto 0);
signal SUM_NO_CARRY : std_logic_vector((BITCOUNT-1) downto 0);
begin
GENERATION <= X and Y;
PROPAGATION <= X or Y;
SUM_NO_CARRY <= X xor Y;
CARRY_LOOK_AHEAD_PROCESS : process (GENERATION, PROPAGATION, CARRY_IN)
variable C : std_logic;
begin
C := carry_in;
carry(0) <= C;
C := CARRY_IN;
CARRY(0) <= C;
for i in 1 to (BITCOUNT-1) loop
C := generation(i-1) or (propagation(i-1) and C);
carry(i) <= C;
C := GENERATION(i-1) or (PROPAGATION(i-1) and C);
CARRY(i) <= C;
end loop;
end process;
result <= sum_no_carry xor carry;
carry_out <= (X(BITCOUNT-1) and Y(BITCOUNT-1)) or (X(BITCOUNT-1) and carry(BITCOUNT-1)) or (carry(BITCOUNT-1) and Y(BITCOUNT-1));
RESULT <= SUM_NO_CARRY xor CARRY;
CARRY_OUT <= (X(BITCOUNT-1) and Y(BITCOUNT-1)) or (X(BITCOUNT-1) and CARRY(BITCOUNT-1)) or (CARRY(BITCOUNT-1) and Y(BITCOUNT-1));
end CarryLookAheadArch;