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- 30th October 2006, 18:49 #1

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## vhdl comparator

I want to design a 2-bit comparator using VHDL that takes two unsigned std_logic_vectrors A and B and produces bits L,G,E, where

L=1 , if A<B

G=1, if A>B

E=1, if A=B

Then Using VHDL, I want to design an 8-bit comparator that uses the 2-bit .the 8bit comparator should have two 8-bit registers that load the inputs on the rising edge of the clock and one 3bit register that loads the outputs on the falling edge of the clock.

- 30th October 2006, 18:49

- 31st October 2006, 07:21 #2

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## comparator vhdl

Here it goes ... Hope this helps!

Code:library ieee; use ieee.std_logic_1164.all; entity comparator is port ( A : in std_logic_vector(1 downto 0); B : in std_logic_vector(1 downto 0); L_in : in std_logic; G_in : in std_logic; E_in : in std_logic; L : out std_logic; G : out std_logic; E : out std_logic); end comparator; architecture behav of comparator is begin -- behav process (A, B, L_in, G_in, E_in) begin -- process if ( (A = B) and E_in = '1') then E <= '1'; else E <= '0'; end if; if (A(1)= '1' and B(1) = '0') or ( (A(1) = B(1)) and (A(0)='1' and B(0)= '0')) or ((A = B) and G_in = '1') then G <= '1'; else G <= '0'; end if; if (A(1)='0' and B(1) ='1') or ((A(1) = B(1)) and A(0)='0' and B(0)= '1') or ((A = B) and L_in = '1') then L <= '1'; else L <= '0'; end if; end process; end behav; library ieee; use ieee.std_logic_1164.all; entity comp_8bit is port ( A : in std_logic_vector(7 downto 0); B : in std_logic_vector(7 downto 0); L : out std_logic; G : out std_logic; E : out std_logic); end comp_8bit; architecture struct of comp_8bit is component comparator port ( A : in std_logic_vector(1 downto 0); B : in std_logic_vector(1 downto 0); L_in : in std_logic; G_in : in std_logic; E_in : in std_logic; L : out std_logic; G : out std_logic; E : out std_logic); end component; signal E_0, E_1, E_2, L_0, L_1, L_2, G_0, G_1, G_2 : std_logic; begin -- struct u1 : comparator port map ( A => A(1 downto 0), B => B(1 downto 0), L_in => '0', G_in => '0', E_in => '1', G => G_0, L => L_0, E => E_0); u2 : comparator port map ( A => A(3 downto 2), B => B(3 downto 2), G_in => G_0, L_in => L_0, E_in => E_0, G => G_1, L => L_1, E => E_1); u3 : comparator port map ( A => A(5 downto 4), B => B(5 downto 4), G_in => G_1, L_in => L_1, E_in => E_1, L => L_2, E => E_2); u4 : comparator port map ( A => A(7 downto 6), B => B(7 downto 6), G_in => G_2, L_in => L_2, E_in => E_2, L => L, G => G, E => E); end struct;

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