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[/] [am9080_cpu_based_on_microcoded_am29xx_bit-slices/] [trunk/] [acia.vhd] - Rev 8
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---------------------------------------------------------------------------------- -- Company: -- Engineer: -- -- Create Date: 11:56:00 11/12/2017 -- Design Name: -- Module Name: ACIA - Behavioral -- Project Name: -- Target Devices: -- Tool versions: -- Description: Simple wrapper around https://github.com/jakubcabal/uart-for-fpga -- -- Dependencies: -- -- Revision: -- Revision 0.01 - File Created -- Additional Comments: -- ---------------------------------------------------------------------------------- library IEEE; use IEEE.STD_LOGIC_1164.ALL; -- Uncomment the following library declaration if using -- arithmetic functions with Signed or Unsigned values use IEEE.NUMERIC_STD.ALL; -- Uncomment the following library declaration if instantiating -- any Xilinx primitives in this code. --library UNISIM; --use UNISIM.VComponents.all; entity ACIA is Port ( clk: in std_logic; reset: in std_logic; D : inout STD_LOGIC_VECTOR (7 downto 0); A : in STD_LOGIC; nRead : in STD_LOGIC; nWrite : in STD_LOGIC; nSelect : in STD_LOGIC; IntReq: buffer std_logic; IntAck: in STD_LOGIC; txd: out std_logic; rxd: in std_logic); end ACIA; architecture Behavioral of ACIA is -- -- https://github.com/jakubcabal/uart-for-fpga -- component UART is Generic ( CLK_FREQ : integer := 50e6; -- system clock frequency in Hz BAUD_RATE : integer := 115200; -- baud rate value PARITY_BIT : string := "none"; -- type of parity: "none", "even", "odd", "mark", "space" USE_DEBOUNCER : boolean := True -- enable/disable debouncer ); Port ( CLK : in std_logic; -- system clock RST : in std_logic; -- high active synchronous reset -- UART INTERFACE UART_TXD : out std_logic; -- serial transmit data UART_RXD : in std_logic; -- serial receive data -- USER DATA INPUT INTERFACE DATA_IN : in std_logic_vector(7 downto 0); -- input data DATA_SEND : in std_logic; -- when DATA_SEND = 1, input data are valid and will be transmit BUSY : out std_logic; -- when BUSY = 1, transmitter is busy and you must not set DATA_SEND to 1 -- USER DATA OUTPUT INTERFACE DATA_OUT : out std_logic_vector(7 downto 0); -- output data DATA_VLD : out std_logic; -- when DATA_VLD = 1, output data are valid FRAME_ERROR : out std_logic -- when FRAME_ERROR = 1, stop bit was invalid ); end component; signal d_out, rxd_data: std_logic_vector(7 downto 0); signal rd_data, wr_data, wr_data0, wr_data1, rd_status, data_send: std_logic; signal readSelect, writeSelect: std_logic; signal valid, busy, error, char_received, ready: std_logic; signal status_valid, status_error: std_logic; begin readSelect <= nSelect nor nRead; writeSelect <= nSelect nor nWrite; wr_data <= writeSelect and A; rd_data <= readSelect and A ; rd_status <= readSelect and not(A); D <= d_out when (readSelect = '1') else "ZZZZZZZZ"; d_out <= rxd_data when (A = '1') else (IntReq & status_error & "0000" & ready & status_valid); sio: UART generic map ( --CLK_FREQ => 100e6, BAUD_RATE => 38400 -- science fiction for the 80ies era... --PARITY_BIT => "even" ) port map ( CLK => clk, RST => reset, -- UART INTERFACE UART_TXD => txd, -- serial transmit data UART_RXD => rxd, -- serial receive data -- USER DATA INPUT INTERFACE DATA_IN => D, DATA_SEND => data_send, BUSY => busy, -- USER DATA OUTPUT INTERFACE DATA_OUT => rxd_data, DATA_VLD => valid, FRAME_ERROR => error ); ready <= not busy; data_send <= wr_data and not (wr_data1); generate_sendpulse: process(reset, clk, busy, wr_data) begin if (reset = '1') then wr_data0 <= '0'; wr_data1 <= '0'; else if (rising_edge(clk)) then wr_data1 <= wr_data0; wr_data0 <= wr_data; end if; end if; end process; char_received <= valid or error; generate_intreq: process(reset, IntAck, rd_data, char_received) begin if (reset = '1' or IntAck = '1' or rd_data = '1') then IntReq <= '0'; status_error <= not(reset or rd_data); status_valid <= not(reset or rd_data); else if rising_edge(char_received) then IntReq <= '1'; status_error <= error; status_valid <= valid; end if; end if; end process; end Behavioral;
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