Subversion Repositories uart_block

--! uart control unit

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

--! Use CPU Definitions package

use work.pkgDefinitions.all;

entity uart_control is

    Port ( rst : in  STD_LOGIC;                                                                                                         -- Global reset

           clk : in  STD_LOGIC;                                                                                                         -- Global clock

                          WE    : in STD_LOGIC;                                                                                                         -- Write enable

           reg_addr : in  STD_LOGIC_VECTOR (1 downto 0);                                         -- Register address

                          start : in std_logic;                                                                                                         -- Start (Strobe)

                          done : out std_logic;                                                                                                         -- Done (ACK)

           DAT_I : in  STD_LOGIC_VECTOR ((nBitsLarge-1) downto 0);               -- Data Input (Wishbone)

           DAT_O : out  STD_LOGIC_VECTOR ((nBitsLarge-1) downto 0);              -- Data output (Wishbone)

                          baud_wait : out STD_LOGIC_VECTOR ((nBitsLarge-1) downto 0);    -- Signal to control the baud rate frequency

                          data_byte_tx : out std_logic_vector((nBits-1) downto 0);               -- 1 Byte to be send to serial_transmitter

                          data_byte_rx : in std_logic_vector((nBits-1) downto 0);        -- 1 Byte to be received by serial_receiver

           tx_data_sent : in  STD_LOGIC;                                                                                        -- Signal comming from serial_transmitter

           rx_data_ready : in  STD_LOGIC);                                                                              -- Signal comming from serial_receiver

end uart_control;

architecture Behavioral of uart_control is

signal config_clk : std_logic_vector((nBitsLarge-1) downto 0);

signal config_baud : std_logic_vector((nBitsLarge-1) downto 0);

signal byte_to_receive : std_logic_vector((nBits-1) downto 0);

signal byte_to_transmitt : std_logic_vector((nBits-1) downto 0);

signal controlStates : uartControl;

signal sigDivRst : std_logic;

signal sigDivDone : std_logic;

signal sigDivQuotient : std_logic_vector((nBitsLarge-1) downto 0);

signal sigDivReminder : std_logic_vector((nBitsLarge-1) downto 0);

signal sigDivNumerator : std_logic_vector((nBitsLarge-1) downto 0);

signal sigDivDividend : std_logic_vector((nBitsLarge-1) downto 0);

-- Divisor component

component divisor is

    Port ( rst : in  STD_LOGIC;

           clk : in  STD_LOGIC;

           quotient : out  STD_LOGIC_VECTOR ((nBitsLarge-1) downto 0);

                          reminder : out  STD_LOGIC_VECTOR ((nBitsLarge-1) downto 0);

           numerator : in  STD_LOGIC_VECTOR ((nBitsLarge-1) downto 0);

           divident : in  STD_LOGIC_VECTOR ((nBitsLarge-1) downto 0);

           done : out  STD_LOGIC);

end component;

begin

        -- Instantiate block for calculate division

        uDiv : divisor port map (

                rst => sigDivRst,

                clk => clk,

                quotient => sigDivQuotient,

                reminder => sigDivReminder,

                numerator => sigDivNumerator,

                divident => sigDivDividend,

                done => sigDivDone

        );

        -- Process that read uart control registers

        process (rst, clk, reg_addr,WE)

        begin

                if rising_edge(clk) then

                        if (WE = '0') and (start = '1') then

                                case reg_addr is

                                        when "00" =>

                                                DAT_O <= config_clk;

                                        when "01" =>

                                                DAT_O <= config_baud;

                                        when "10" =>

                                                -- Byte that will be transmitted

                                                DAT_O <= "000000000000000000000000" & byte_to_transmitt;

                                        when "11" =>

                                                -- Byte that will be received

                                                DAT_O <= "000000000000000000000000" & byte_to_receive;

                                        when others =>

                                                null;

                                end case;

                        end if;

                end if;

        end process;

        -- Process that populate the uart control registers

        process (rst, clk, reg_addr,WE)

        begin

                if rst = '1' then

                        config_clk <= (others => '0');

                        config_baud <= (others => '0');

                        byte_to_transmitt <= (others => '0');

                elsif rising_edge(clk) then

                        if (WE = '1') and (start = '1') then

                                case reg_addr is

                                        when "00" =>

                                                config_clk <= DAT_I;

                                        when "01" =>

                                                config_baud <= DAT_I;

                                        when "10" =>

                                                -- Byte that will be transmitted

                                                byte_to_transmitt <= DAT_I((nBits-1) downto 0);

                                        when others =>

                                                null;

                                end case;

                        end if;

                end if;

        end process;

        -- Process to handle the next state logic

        process (rst, clk, reg_addr, WE)

        variable baud_configured : std_logic;

        variable clk_configured : std_logic;

        variable div_result_baud_wait : std_logic_vector ((nBitsLarge-1) downto 0);

        begin

                if rst = '1' then

                        controlStates <= idle;

                        baud_configured := '0';

                        clk_configured := '0';

                        div_result_baud_wait := (others => '0');

                        done <= '0';

                elsif rising_edge(clk) then

                        case controlStates is

                                when idle =>

                                        done <= '0';

                                        -- Go to config state

                                        if (reg_addr = "00") and (WE = '1') then

                                                controlStates <= config_state_clk;

                                                clk_configured := '1';

                                        elsif (reg_addr = "01") and (WE = '1') then

                                                controlStates <= config_state_baud;

                                                baud_configured := '1';

                                        end if;

                                when config_state_clk =>

                                        sigDivRst <= '1';

                                        sigDivNumerator <= config_clk;

                                        if baud_configured = '0' then

                                                -- Baud not configured yet so wait for it...

                                                controlStates <= idle;

                                                done <= '1';

                                        else

                                                -- If already configured wait for division completion...

                                                controlStates <= start_division;

                                        end if;

                                when config_state_baud =>

                                        sigDivRst <= '1';

                                        sigDivDividend <= config_baud;

                                        if clk_configured = '0' then

                                                -- Clock not configured yet so wait for it...

                                                controlStates <= idle;

                                                done <= '1';

                                        else

                                                -- If already configured wait for division completion...

                                                controlStates <= start_division;

                                        end if;

                                when start_division =>

                                        sigDivRst <= '0';

                                        controlStates <= wait_division;

                                when wait_division =>

                                        if sigDivDone = '0' then

                                                controlStates <= wait_division;

                                        else

                                                -- Division done, get the result to put on the wait_cycles signal of the baud generator

                                                div_result_baud_wait := sigDivQuotient;

                                                controlStates <= config_state_baud_generator;

                                        end if;

                                when config_state_baud_generator =>

                                        -- Configure the wait_cycle for the desired baud rate...

                                        baud_wait <= div_result_baud_wait;

                                        controlStates <= rx_tx_state;

                                        done <= '1';

                                -- Control the serial_receiver or serial_transmitter block

                                when rx_tx_state =>

                                        controlStates <= rx_tx_state;

                                        if (WE = '1') and (start = '1') then

                                                if reg_addr = "10" then

                                                        controlStates <= tx_state_wait;

                                                        done <= '0';

                                                end if;

                                        end if;

                                        if (WE = '0') and (start = '1') then

                                                if reg_addr = "11" then

                                                        controlStates <= rx_state_wait;

                                                        done <= '0';

                                                end if;

                                        end if;

                                -- Send data and wait to transmit

                                when tx_state_wait =>

                                        data_byte_tx <= byte_to_transmitt;

                                        if tx_data_sent = '0' then

                                                controlStates <= tx_state_wait;

                                        else

                                                controlStates <= rx_tx_state;

                                                done <= '1';

                                        end if;

                                -- Receive data and wait to receive

                                when rx_state_wait =>

                                        if rx_data_ready = '1' then

                                                byte_to_receive <= data_byte_rx;

                                                done <= '1';

                                                controlStates <= rx_tx_state;

                                        else

                                                controlStates <= rx_state_wait;

                                        end if;

                        end case;

                end if;

        end process;

end Behavioral;