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Altera_Forum's avatar
Altera_Forum
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12 years ago

How to make vhdl testbench for mux 4 to 1 and inputs are 4bits and output is 4bit

Hi!

I have problem to make vhdl testbench for mux4/1 witch have 4bit inputs I0 I1 I2 I3 and 4bit output mux_out and select inputs are KO and K1.

REMARK:

I0 : in std_logic_vector (3 downto 0)

I1: in std_logic_vector (3 downto 0)

I2: in std_logic_vector (3 downto 0)

I3: in std_logic_vector (3 downto 0)

mux_out : out std_logic_vector (3 downto 0)

KO,K1: in std_logic

So, behind the multiplexer I have four components witch outputs are also 4bit and each 4bit output from component goes to one 4bit input of the multiplexer.

So, I can not put value of inputs multiplexer in test bench because I have to bring only outputs from components witch are already defined with their functions.

I hope that you understand me.

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    --- Quote Start ---

    I dont understand.

    Please post some code.

    --- Quote End ---

    I think the post means that they want to test part of the design(the mux).

    so if that is the case either test the mux alone as a separate module with its i/o interface exposed out, or just use full design and temporarily disconnect drive on mux inputs and drive them in the testbench
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    THIS IS MULTIPLEXER 4/1

    library IEEE;

    use IEEE.STD_LOGIC_1164.ALL;

    entity multiplexer_four_one is

    port (

    I0 : in std_logic_vector (3 downto 0);

    I1 : in std_logic_vector (3 downto 0);

    I2 : in std_logic_vector (3 downto 0);

    I3 : in std_logic_vector (3 downto 0);

    sel :in std_logic_vector (1 downto 0);

    mux_out : out std_logic_vector (3 downto 0)

    );

    end multiplexer_four_one;

    architecture Behavioral of multiplexer_four_one is

    begin

    process(I0,I1,I2,I3,sel)

    begin

    case sel is

    when "00" => mux_out <= I0;

    when "01" => mux_out <= I1;

    when "10" => mux_out <= I2;

    when "11" => mux_out <= I3;

    end case;

    end process;

    end Behavioral;

    I need to make 4bit ALU with adder/substract and others components which I will give in text.

    SO , I first make 4bit adder/sub with 4bit inputs A and B(that inputs goes also on other inputs components,so its 4bit) like the first component, then the second component is 4bit xor gate with 4bit input/output, the third component is 4bit shift_left

    The fourth component is inverter . This four component work some operations. SO after that I have to make ALU unit with multiplexer which will allow some of this components operation

    on the outputs of multiplexer Inputs of multiplexer ( I0 I1 I2 I 3 ) are connected with outputs of components.The each input of multiplexer should be connected with 4bit outputs of components. Then inputs of multiplexer must bi 4bit !!!!!!!

    So that, select inputs of MUX which is sel in code will allow for example for sel="00" then shift left on the output 4bit signal

    Thus, I have problem to make test bench for that ALU respectively multiplexer because hi is indeed ALU. OK?

    I do not understand how to give time signal for simulation mux (ALU) in test bench.

    DO YOU UNDERSTAND NOW???