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Altera_Forum's avatar
Altera_Forum
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8 years ago

Generate a bianry code from an integer array?

Hello!

I am trying to work for first time with integer arrays. I am not so used to work with them, and I am not able to compile my code.

At first, I have created a package, for the arrays of integers:

--- Quote Start ---

LIBRARY ieee;

USE ieee.std_logic_1164.all;

USE ieee.numeric_std.all;

PACKAGE inputnumberrs IS

constant longitude : integer := 4;

type num is array (longitude-1 to 0) of integer;

END;

--- Quote End ---

BTW, I suppose that I will be able to modify this "longitude" constant for another number in ModelSim, right? Forcing the signal or something i suppose.

Then, I have created the entity of another project:

--- Quote Start ---

entity generator is

generic (longitude : integer := 4);

port (X, Y : in num;

clk : in std_logic);

end generator;

--- Quote End ---

And what I want to do is, for example, itroducing 2314 to X and to generate "0010 0011 0001 0100", so I have tryied this:

--- Quote Start ---

architecture Behavioral of generator is

signal t, u : integer := 0;

signal a,b : std_logic_vector (longitude*longitude downto 0);

begin

process

begin

wait until CLK'EVENT and CLK = '1';

for i in 0 to (longitud*longitud) loop

a(u)<= std_logic_vector(to_unsigned(x,4));

t<= t+1;

u <= u + 4 ;

end loop;

wait;

end process;

end behavioral;

--- Quote End ---

The compilation error I get is : Error (10409): VHDL Type Conversion error at generar_numeros.vhd(40): converted type of object near text or symbol "std_logic_vector" must match std_ulogic type of target object

and i do not have any idea why it is not compiling. If I write a <= std_logic_vector(to_unsigned(x,4)); , withouth the (U), it compiles but does not work :( Any suggestions?

2 Replies

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

    Several issues in the code:

    1. Your Num type is a null array (ie, it has 0 length)

    type num is array (longitude-1 to 0) of integer;

    This is a null array, so has length 0. with an ascending array (using to), the larger number must be on the right. So you need to use:

    type num is array (0 to longitude-1) of integer;

    A a descending array (using downto) is the opposite.

    2. You have a longitude generic, but the length of the num type is set in the package. So having longitude generic set to anything other than 4 will not work. PS. having a generic called longitude means you've hidden the longitude constant in the inputnumberrs package

    3. Your a and b slvs are (16 downto 0) ie. 17 bits long. Did you forget the -1?

    4. a(u) is a single bit, the 0th element of the a slv. Also, x is an array of integers. to_unsigned only convers a single integer. You also are using the literal 4, when you should probably be using the generic or constant (see issues above)

    5. why have you got a for loop, when you dont use the loop variable, i?

    6. I assume this is test code, as this will not synthesis as you have a wait statement at the end of the process. So on the first clock, you set a value of A, and then thats it?

    7. t is unused.

    a <= std_logic_vector(to_unsigned(x,4)) cannot be working with the code you posted, as X is an array of 4 integers, and no to_unsigned function exists to convert multiple integers, unless you have defined it yourself.

    So, is this just test code? it cannot work on an FPGA.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    You are assigning a bit vector to a single bit which isn't possible, a simple issue of VHDL syntax.

    You want to write something like 

    a(u+3 downto u)<= std_logic_vector(to_unsigned(x,4));

    --- Quote Start ---

    And what I want to do is, for example, introducing 2314 to X and to generate "0010 0011 0001 0100", so I have tryied this:

    --- Quote End ---

    2314 isn't an array of integer literal, it's either a decimal value or a string respectively character array.