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-- Company:

-- Engineer:

--

-- Create Date:    16:16:02 05/14/2014

-- Design Name:    Configurable ANN

-- Module Name:    activation_function - Structural

-- Project Name:

-- Target Devices:

-- Tool versions:

-- Description: Activation function selector. It instantiates the activation

--             funtion type selected with f_type parameter.

--

-- Dependencies:

--

-- Revision:

-- Revision 0.01 - File Created

-- Additional Comments:

--

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library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

entity activation_function is

   generic

   (

      lsbit : natural := 10;

      f_type : string := "linear"; -- Activation function type

      Nbit   : natural := 8        -- Bit width

   );

   port

   (

      reset   : in  std_logic;

      clk     : in  std_logic;

      run_in  : in  std_logic; -- Start and input data validation

      inputs  : in  std_logic_vector(Nbit-1 downto 0); -- Input data

      run_out : out std_logic; -- Output data validation, run_in for the next layer

      outputs : out std_logic_vector(Nbit-1 downto 0)  -- Output data

   );

end activation_function;

architecture Structural of activation_function is

begin

-- Linear activation function. It is a direct assignment:

linear_f:

   if (f_type = "linear") generate

      outputs <= inputs;

      run_out <= run_in;

   end generate;

-- Example 1: sigmoid activation function implemented as a Look-Up-Table (LUT):

Sigmoid_f:

   if (f_type = "siglut") generate

      siglut_inst: entity work.af_sigmoid

         generic map

         (

            Nbit => Nbit

         )

         port map

         (

            reset   => reset,

            clk     => clk,

            run_in  => run_in,

            inputs  => inputs,

            run_out => run_out,

            outputs => outputs

         );

   end generate;

-- Example 2: sigmoid activation function implemented as a LUT, with a second different set of parameters:

Sigmoid2_f:

   if (f_type = "siglu2") generate

      siglut_inst: entity work.af_sigmoid2

         generic map

         (

            Nbit => Nbit

         )

         port map

         (

            reset   => reset,

            clk     => clk,

            run_in  => run_in,

            inputs  => inputs,

            run_out => run_out,

            outputs => outputs

         );

   end generate;

-- Example 3: sigmoid activation function implemented as a LUT, with a second different set of parameters:

sigmoid_mat:

   if (f_type = "sigmat") generate

      siglut_inst: entity work.af_sigmoid_mat

         generic map

         (

            Nbit  => Nbit,

            lsbit => lsbit

         )

         port map

         (

            reset   => reset,

            clk     => clk,

            run_in  => run_in,

            inputs  => inputs,

            run_out => run_out,

            outputs => outputs

         );

   end generate;

-- Template to instance user activation function type ("userAF"):

--userAF_f:

   --if (f_type = "userAF") generate

      --yourAF_inst: entity work.--palace here user module name--

         --generic map

         --(

         --   Nbits => Nbits

         --)

         --port map

         --(

         --   reset => reset,

         --   clk   => clk,

         --   run_in  => run_in,

         --   inputs  => inputs,

         --   run_out => run_out,

         --   outputs => outputs

         --);

   --end generate;

-- User can instantiate as many types of activation function as needed, each one of them must be tagged as a 6 character string

end Structural;