Random Numbers in VHDL

Here’s the translation of the Go random numbers example to VHDL:

Our program will demonstrate generating random numbers. Here’s the full source code:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity RandomNumbers is
end RandomNumbers;

architecture Behavioral of RandomNumbers is
    -- Define a function to generate a pseudo-random number
    function rand_int(seed : integer) return integer is
        variable x : integer := seed;
    begin
        x := (x * 1103515245 + 12345) mod 2147483648;
        return x;
    end function;

    signal seed : integer := 42;
begin
    process
        variable rand_num : integer;
    begin
        -- Generate random integers
        rand_num := rand_int(seed) mod 100;
        report "Random integer 1: " & integer'image(rand_num);
        
        seed <= rand_int(seed);
        rand_num := rand_int(seed) mod 100;
        report "Random integer 2: " & integer'image(rand_num);
        
        -- Generate random real numbers between 0 and 1
        rand_num := rand_int(seed);
        report "Random real: " & real'image(real(rand_num) / real(2147483648));
        
        -- Generate random real numbers between 5 and 10
        seed <= rand_int(seed);
        rand_num := rand_int(seed);
        report "Random real (5-10): " & real'image((real(rand_num) / real(2147483648)) * 5.0 + 5.0);
        
        wait;
    end process;
end Behavioral;

This VHDL code demonstrates the concept of generating random numbers. Since VHDL doesn’t have a built-in random number generator, we’ve implemented a simple pseudo-random number generator using the linear congruential method.

The rand_int function generates a pseudo-random integer based on a seed value. We use this to create random integers and then convert them to real numbers in different ranges.

To run this VHDL code, you would typically use a VHDL simulator. The output will be in the form of report statements, which will appear in the simulator’s console or log.

Note that this is a simplified example and not suitable for cryptographic purposes. In real VHDL applications, especially for hardware design, you might use more sophisticated random number generation techniques or dedicated IP cores for random number generation.

The concept of seeded random number generation is maintained, allowing for reproducible sequences of random numbers when the same seed is used.

For more advanced random number generation in VHDL, you might want to look into specialized libraries or IP cores designed for FPGA implementations.