Subversion Repositories multiply-accumulate

LIBRARY ieee;

USE ieee.std_logic_1164.ALL;

USE ieee.numeric_std.ALL;

ENTITY mac IS

        GENERIC (n   :   INTEGER := 4); --define X and Y size 

        PORT (

                ck  : IN  STD_LOGIC;

                rst : IN  STD_LOGIC;

                X   : IN  SIGNED (n-1 DOWNTO 0); --n

                Y   : IN  SIGNED (n-1 DOWNTO 0); --n

                A   : OUT SIGNED ((2+2*n)-1 DOWNTO 0)  --2+2n (include two leading bits for overflow)

        );

END mac;

ARCHITECTURE hdl OF mac IS

        SIGNAL acc : SIGNED ((2+2*n)-1 DOWNTO 0) := (OTHERS => '0'); --2+2n

BEGIN

        PROCESS (ck)

        BEGIN

                IF rising_edge(ck) THEN

                        IF rst ='0' THEN --reset accumulator at low

                                acc <= (OTHERS => '0');

                        ELSE

                                acc <= acc + shift_left(X * Y, 1);

                        END IF;

                END IF;

        END PROCESS;

        A <= acc;

END hdl;