CODEWITHSUNDEEP
randomfpga
stone
stone

Reputation:

How to generate pseudo random number in FPGA?

How to generate pseudo random number in FPGA?

Upvotes: 8

Views: 20172

Answers (5)

Pedro_Uno
Pedro_Uno

Reputation: 1052

If you need a randomized word, like the C rand() function, an LFSR by itself will not do the job. I made a little open-source FPGA rand() module for that purpose.

It is parameterized for initial state and output width. It is written to use the Xilinx DSP48 core and runs very fast. A single DSP48 gives good results compared to the Mersenne Twister.

https://github.com/hdlguy/pg_prng

This project also contains parameterized LFSR modules if that's what you need.

Upvotes: 0

mksuth
mksuth

Reputation: 2029

As others have said, LFSRs can be used for pseudo random numbers in an FPGA. Here is a VHDL implementation of a maximal length 32-bit LFSR.

process(clk)

  -- maximal length 32-bit xnor LFSR based on xilinx app note XAPP210
  function lfsr32(x : std_logic_vector(31 downto 0)) return std_logic_vector is
  begin
    return x(30 downto 0) & (x(0) xnor x(1) xnor x(21) xnor x(31));
  end function;

begin
  if rising_edge(clk) then
    if rst='1' then
      pseudo_rand <= (others => '0');
    else
      pseudo_rand <= lfsr32(psuedo_rand);
    end if;
  end if;
end process;

Upvotes: 1

geschema
geschema

Reputation: 2494

There's an excellent Xilinx application note on generating pseudo-random number sequences efficiently in an FPGA. It's XAPP052.

Upvotes: 5

starblue
starblue

Reputation: 56762

If it's not for cryptography or other applications with an intelligent adversary (e.g. gambling) I'd use a linear feedback shift register approach.

It only uses exclusive or and shift, so it is very simple to implement in hardware.

Upvotes: 4

Marty
Marty

Reputation: 6644

This has been covered (I'd go for an LFSR): Random number generation on Spartan-3E

Upvotes: 7

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