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--

--      Input file         : wb_stdio.vhd

--      Design name        : wb_stdio

--      Author             : Tamar Kranenburg

--      Company            : Delft University of Technology

--                         : Faculty EEMCS, Department ME&CE

--                         : Systems and Circuits group

--

--      Description        : Simulates standard output using stdio package

--

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library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

library mblite;

use mblite.config_Pkg.all;

use mblite.core_Pkg.all;

use mblite.std_Pkg.all;

use std.textio.all;

entity wb_stdio is port

(

    wb_o : out wb_slv_out_type;

    wb_i : in wb_slv_in_type

);

end wb_stdio;

architecture arch of wb_stdio is

    constant ack_assert_delay : TIME := 2 ns;

    constant ack_deassert_delay : TIME := 2 ns;

    signal ack : std_logic;

    signal chr_dat : std_logic_vector(31 downto 0);

    signal chr_cnt : natural := 0;

begin

    wb_o.int_o <= '0';

    wb_o.dat_o <= chr_dat;

    -- Character device

    stdio: process(wb_i.clk_i)

        variable s    : line;

        variable byte : std_logic_vector(7 downto 0);

        variable char : character;

    begin

        if rising_edge(wb_i.clk_i) then

            if (wb_i.stb_i and wb_i.cyc_i) = '1' then

                if wb_i.we_i = '1' and ack = '0' then

                -- WRITE STDOUT

                    wb_o.ack_o <= '1' after ack_assert_delay;

                    ack <= '1';

                    case wb_i.sel_i is

                        when "0001" => byte := wb_i.dat_i( 7 downto 0);

                        when "0010" => byte := wb_i.dat_i(15 downto 8);

                        when "0100" => byte := wb_i.dat_i(23 downto 16);

                        when "1000" => byte := wb_i.dat_i(31 downto 24);

                        when others => null;

                    end case;

                    char := character'val(my_conv_integer(byte));

                    if byte = X"0D" then

                        -- Ignore character 13

                    elsif byte = X"0A" then

                        -- Writeline on character 10 (newline)

                        writeline(output, s);

                    else

                        -- Write to buffer

                        write(s, char);

                    end if;

                elsif ack = '0' then

                -- READ stdout

                    ack <= '1';

                    wb_o.ack_o <= '1' after ack_assert_delay;

                    if chr_cnt = 0 then

                        chr_cnt <= 1;

                        chr_dat <= X"4C4C4C4C";

                    elsif chr_cnt = 1 then

                        chr_cnt <= 2;

                        chr_dat <= X"4D4D4D4D";

                    elsif chr_cnt = 2 then

                        chr_cnt <= 3;

                        chr_dat <= X"4E4E4E4E";

                    elsif chr_cnt = 3 then

                        chr_cnt <= 0;

                        chr_dat <= X"0A0A0A0A";

                    end if;

                end if;

            else

                ack <= '0';

                wb_o.ack_o <= '0' after ack_deassert_delay;

            end if;

        end if;

    end process;

end arch;