Subversion Repositories gpib_controller

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-- Entity: gpibReader

-- Date: 2011-10-30  

-- Author: apaluch

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library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

use ieee.std_logic_arith.all;

use work.utilPkg.all;

entity gpibReader is

        port (

                -- clock

                clk : in std_logic;

                -- reset

                reset : std_logic;

                ------------------------------------------------------------------------

                ------ GPIB interface --------------------------------------------------

                ------------------------------------------------------------------------

                -- input data

                data_in : in std_logic_vector (7 downto 0);

                -- data valid

                dvd : in std_logic;

                -- listener active

                lac : in std_logic;

                -- last byte

                lsb : in std_logic;

                -- ready to next byte

                rdy : out std_logic;

                ------------------------------------------------------------------------

                ------ external interface ----------------------------------------------

                ------------------------------------------------------------------------

                -- is LE function active

                isLE : in std_logic;

                -- current secondary address

                secAddr : in std_logic_vector (4 downto 0);

                -- secondary address of data

                dataSecAddr : out std_logic_vector (4 downto 0);

                -- buffer ready interrupt

                buf_interrupt : out std_logic;

                -- indicates end of stream

                end_of_stream : out std_logic;

                -- resets reader

                reset_reader : in std_logic;

                ------------------ fifo --------------------------------------

                -- indicates fifo full

                fifo_full : in std_logic;

                -- indicates fifo ready to write

                fifo_ready_to_write : in std_logic;

                -- indicates at least one byte in fifo

                at_least_one_byte_in_fifo : in std_logic;

                -- output data

                data_out : out std_logic_vector (7 downto 0);

                -- fifo strobe

                fifo_strobe : out std_logic

        );

end gpibReader;

architecture arch of gpibReader is

        -- reader states

        type READER_STATE is (

                ST_IDLE,

                ST_WAIT_DVD_1,

                ST_WAIT_DVD_0

        );

        signal current_state : READER_STATE;

        signal buf_ready_to_write : boolean;

begin

        buf_interrupt <= not to_stdl(buf_ready_to_write);

        process (clk, reset, reset_reader) begin

                if reset = '1' then

                        current_state <= ST_IDLE;

                        rdy <= '1';

                        buf_ready_to_write <= TRUE;

                        end_of_stream <= '0';

                        fifo_strobe <= '0';

                        dataSecAddr <= "00000";

                elsif reset_reader='1' then

                        buf_ready_to_write <= TRUE;

                        end_of_stream <= '0';

                        fifo_strobe <= '0';

                        dataSecAddr <= "00000";

                elsif rising_edge(clk) then

                        case current_state is

                                when ST_IDLE =>

                                        if lac='1' and buf_ready_to_write then

                                                if isLE = '1' then

                                                        dataSecAddr <= secAddr;

                                                end if;

                                                rdy <= '1';

                                                current_state <= ST_WAIT_DVD_1;

                                        elsif lac='0' and at_least_one_byte_in_fifo='1' then

                                                buf_ready_to_write <= FALSE;

                                        end if;

                                when ST_WAIT_DVD_1 =>

                                        if dvd='1' and fifo_ready_to_write='1' then

                                                fifo_strobe <= '1';

                                                data_out <= data_in;

                                                if lsb='1'or fifo_full='1' then

                                                        buf_ready_to_write <= FALSE;

                                                        end_of_stream <= lsb;

                                                end if;

                                                rdy <= '0';

                                                current_state <= ST_WAIT_DVD_0;

                                        elsif lac='0' then

                                                current_state <= ST_IDLE;

                                        end if;

                                when ST_WAIT_DVD_0 =>

                                        if dvd='0' then

                                                fifo_strobe <= '0';

                                                current_state <= ST_IDLE;

                                        end if;

                                when others =>

                                        current_state <= ST_IDLE;

                        end case;

                end if;

        end process;

end arch;