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MyHDL[1] is a Python based hardware description language (HDL).

Features of MyHDL include:

  • The ability to generate VHDL and Verilog code from a MyHDL design.[2]
  • The ability to generate a testbench (Conversion of test benches[3]) with test vectors in VHDL or Verilog, based on complex computations in Python.
  • The ability to convert a lists of signals.[4]
  • The ability to convert output verification.[5]
  • The ability to do Co-simulation with Verilog.[6]
  • An advanced datatype system, independent of traditional datatypes. MyHDL's translator tool automatically writes conversion functions when the target language requires them.

MyHDL is developed by Jan Decaluwe.[7]

Conversion Examples[edit]

Here, you can see some examples of conversions from MyHDL designs to VHDL and/or Verilog.[8]

A small combinatorial design

The example is a small combinatorial design, more specifically the binary to Gray code converter:

def bin2gray(B, G, width):

    """ Gray encoder.

    B -- input intbv signal, binary encoded
    G -- output intbv signal, gray encoded
    width -- bit width


    def logic():
        Bext = intbv(0)[width+1:]
        Bext[:] = B
        for i in range(width):
  [i] = Bext[i+1] ^ Bext[i]

    return logic

You can create an instance and convert to Verilog and VHDL as follows:

width = 8

B = Signal(intbv(0)[width:])
G = Signal(intbv(0)[width:])

bin2gray_inst = toVerilog(bin2gray, B, G, width)
bin2gray_inst = toVHDL(bin2gray, B, G, width)

The generated Verilog code looks as follows:

module bin2gray (

input [7:0] B;
output [7:0] G;
reg [7:0] G;

always @(B) begin: BIN2GRAY_LOGIC
    integer i;
    reg [9-1:0] Bext;
    Bext = 9'h0;
    Bext = B;
    for (i=0; i<8; i=i+1) begin
        G[i] <= (Bext[(i + 1)] ^ Bext[i]);


The generated VHDL code looks as follows:

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
use std.textio.all;

use work.pck_myhdl_06.all;

entity bin2gray is
    port (
        B: in unsigned(7 downto 0);
        G: out unsigned(7 downto 0)
end entity bin2gray;

architecture MyHDL of bin2gray is


BIN2GRAY_LOGIC: process (B) is
    variable Bext: unsigned(8 downto 0);
    Bext := to_unsigned(0, 9);
    Bext := resize(B, 9);
    for i in 0 to 8-1 loop
        G(i) <= (Bext((i + 1)) xor Bext(i));
    end loop;
end process BIN2GRAY_LOGIC;

end architecture MyHDL;

See also[edit]