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[/] [neorv32/] [trunk/] [rtl/] [core/] [neorv32_uart.vhd] - Rev 44
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-- ################################################################################################# -- # << NEORV32 - Universal Asynchronous Receiver and Transmitter (UART) >> # -- # ********************************************************************************************* # -- # Frame configuration: 1 start bit, 8 bit data, optional parity bit (even/odd), 1 stop bit, # -- # programmable BAUD rate via clock pre-scaler and BAUD value config register. # -- # Interrupt: UART_RX_available or UART_TX_done # -- # # -- # SIMULATION: # -- # When the simulation mode is enabled (setting the ctrl.ctrl_uart_sim_en_c bit) any write # -- # access to the TX register will not trigger any UART activity. Instead, the written data is # -- # output to the simulation environment. The lowest 8 bits of the written data are printed as # -- # ASCII char to the simulator console. This char is also stored to a text file # -- # "neorv32.uart.sim_mode.text.out". The full 32-bit write data is also stored as 8-hex char # -- # encoded value to text file "neorv32.uart.sim_mode.data.out". # -- # ********************************************************************************************* # -- # BSD 3-Clause License # -- # # -- # Copyright (c) 2020, Stephan Nolting. All rights reserved. # -- # # -- # Redistribution and use in source and binary forms, with or without modification, are # -- # permitted provided that the following conditions are met: # -- # # -- # 1. Redistributions of source code must retain the above copyright notice, this list of # -- # conditions and the following disclaimer. # -- # # -- # 2. Redistributions in binary form must reproduce the above copyright notice, this list of # -- # conditions and the following disclaimer in the documentation and/or other materials # -- # provided with the distribution. # -- # # -- # 3. Neither the name of the copyright holder nor the names of its contributors may be used to # -- # endorse or promote products derived from this software without specific prior written # -- # permission. # -- # # -- # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS # -- # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF # -- # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE # -- # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, # -- # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE # -- # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED # -- # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING # -- # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED # -- # OF THE POSSIBILITY OF SUCH DAMAGE. # -- # ********************************************************************************************* # -- # The NEORV32 Processor - https://github.com/stnolting/neorv32 (c) Stephan Nolting # -- ################################################################################################# library ieee; use ieee.std_logic_1164.all; use ieee.numeric_std.all; library neorv32; use neorv32.neorv32_package.all; use std.textio.all; -- obviously only for simulation entity neorv32_uart is port ( -- host access -- clk_i : in std_ulogic; -- global clock line addr_i : in std_ulogic_vector(31 downto 0); -- address rden_i : in std_ulogic; -- read enable wren_i : in std_ulogic; -- write enable data_i : in std_ulogic_vector(31 downto 0); -- data in data_o : out std_ulogic_vector(31 downto 0); -- data out ack_o : out std_ulogic; -- transfer acknowledge -- clock generator -- clkgen_en_o : out std_ulogic; -- enable clock generator clkgen_i : in std_ulogic_vector(07 downto 0); -- com lines -- uart_txd_o : out std_ulogic; uart_rxd_i : in std_ulogic; -- interrupts -- uart_irq_o : out std_ulogic -- uart rx/tx interrupt ); end neorv32_uart; architecture neorv32_uart_rtl of neorv32_uart is -- simulation output configuration -- constant sim_screen_output_en_c : boolean := true; -- output lowest byte as char to simulator console when enabled constant sim_text_output_en_c : boolean := true; -- output lowest byte as char to text file when enabled constant sim_data_output_en_c : boolean := true; -- dump 32-word to file when enabled -- IO space: module base address -- constant hi_abb_c : natural := index_size_f(io_size_c)-1; -- high address boundary bit constant lo_abb_c : natural := index_size_f(uart_size_c); -- low address boundary bit -- accessible regs -- signal ctrl : std_ulogic_vector(31 downto 0); -- control reg bits -- constant ctrl_uart_baud00_c : natural := 0; -- r/w: UART baud config bit 0 constant ctrl_uart_baud01_c : natural := 1; -- r/w: UART baud config bit 1 constant ctrl_uart_baud02_c : natural := 2; -- r/w: UART baud config bit 2 constant ctrl_uart_baud03_c : natural := 3; -- r/w: UART baud config bit 3 constant ctrl_uart_baud04_c : natural := 4; -- r/w: UART baud config bit 4 constant ctrl_uart_baud05_c : natural := 5; -- r/w: UART baud config bit 5 constant ctrl_uart_baud06_c : natural := 6; -- r/w: UART baud config bit 6 constant ctrl_uart_baud07_c : natural := 7; -- r/w: UART baud config bit 7 -- constant ctrl_uart_baud08_c : natural := 8; -- r/w: UART baud config bit 8 constant ctrl_uart_baud09_c : natural := 9; -- r/w: UART baud config bit 9 constant ctrl_uart_baud10_c : natural := 10; -- r/w: UART baud config bit 10 constant ctrl_uart_baud11_c : natural := 11; -- r/w: UART baud config bit 11 -- constant ctrl_uart_sim_en_c : natural := 12; -- r/w: UART SIMULATION OUTPUT enable -- constant ctrl_uart_pmode0_c : natural := 22; -- r/w: Parity config (0=even; 1=odd) constant ctrl_uart_pmode1_c : natural := 23; -- r/w: Enable parity bit constant ctrl_uart_prsc0_c : natural := 24; -- r/w: UART baud prsc bit 0 constant ctrl_uart_prsc1_c : natural := 25; -- r/w: UART baud prsc bit 1 constant ctrl_uart_prsc2_c : natural := 26; -- r/w: UART baud prsc bit 2 -- constant ctrl_uart_en_c : natural := 28; -- r/w: UART enable constant ctrl_uart_rx_irq_c : natural := 29; -- r/w: UART rx done interrupt enable constant ctrl_uart_tx_irq_c : natural := 30; -- r/w: UART tx done interrupt enable constant ctrl_uart_tx_busy_c : natural := 31; -- r/-: UART transmitter is busy -- data register flags -- constant data_rx_avail_c : natural := 31; -- r/-: Rx data available constant data_rx_overr_c : natural := 30; -- r/-: Rx data overrun constant data_rx_ferr_c : natural := 29; -- r/-: Rx frame error constant data_rx_perr_c : natural := 28; -- r/-: Rx parity error -- access control -- signal acc_en : std_ulogic; -- module access enable signal addr : std_ulogic_vector(31 downto 0); -- access address signal wr_en : std_ulogic; -- word write enable signal rd_en : std_ulogic; -- read enable -- clock generator -- signal uart_clk : std_ulogic; -- numbers of bits in transmission frame -- signal num_bits : std_ulogic_vector(03 downto 0); -- uart tx unit -- type uart_tx_t is record busy : std_ulogic; done : std_ulogic; bitcnt : std_ulogic_vector(03 downto 0); sreg : std_ulogic_vector(10 downto 0); baud_cnt : std_ulogic_vector(11 downto 0); end record; signal uart_tx : uart_tx_t; -- uart rx unit -- type uart_rx_t is record sync : std_ulogic_vector(04 downto 0); avail : std_ulogic_vector(01 downto 0); busy : std_ulogic; busy_ff : std_ulogic; bitcnt : std_ulogic_vector(03 downto 0); sreg : std_ulogic_vector(09 downto 0); data : std_ulogic_vector(07 downto 0); baud_cnt : std_ulogic_vector(11 downto 0); ferr : std_ulogic; -- frame error (stop bit not set) perr : std_ulogic; -- parity error end record; signal uart_rx : uart_rx_t; begin -- Access Control ------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- acc_en <= '1' when (addr_i(hi_abb_c downto lo_abb_c) = uart_base_c(hi_abb_c downto lo_abb_c)) else '0'; addr <= uart_base_c(31 downto lo_abb_c) & addr_i(lo_abb_c-1 downto 2) & "00"; -- word aligned wr_en <= acc_en and wren_i; rd_en <= acc_en and rden_i; -- Read/Write Access ---------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- rw_access: process(clk_i) begin if rising_edge(clk_i) then ack_o <= acc_en and (rden_i or wren_i); -- write access -- if (wr_en = '1') then if (addr = uart_ctrl_addr_c) then ctrl <= (others => '0'); ctrl(ctrl_uart_baud11_c downto ctrl_uart_baud00_c) <= data_i(ctrl_uart_baud11_c downto ctrl_uart_baud00_c); ctrl(ctrl_uart_sim_en_c) <= data_i(ctrl_uart_sim_en_c); ctrl(ctrl_uart_pmode1_c downto ctrl_uart_pmode0_c) <= data_i(ctrl_uart_pmode1_c downto ctrl_uart_pmode0_c); ctrl(ctrl_uart_prsc2_c downto ctrl_uart_prsc0_c) <= data_i(ctrl_uart_prsc2_c downto ctrl_uart_prsc0_c); ctrl(ctrl_uart_en_c) <= data_i(ctrl_uart_en_c); ctrl(ctrl_uart_rx_irq_c) <= data_i(ctrl_uart_rx_irq_c); ctrl(ctrl_uart_tx_irq_c) <= data_i(ctrl_uart_tx_irq_c); end if; end if; -- read access -- data_o <= (others => '0'); if (rd_en = '1') then if (addr = uart_ctrl_addr_c) then data_o(ctrl_uart_baud11_c downto ctrl_uart_baud00_c) <= ctrl(ctrl_uart_baud11_c downto ctrl_uart_baud00_c); data_o(ctrl_uart_sim_en_c) <= ctrl(ctrl_uart_sim_en_c); data_o(ctrl_uart_pmode1_c downto ctrl_uart_pmode0_c) <= ctrl(ctrl_uart_pmode1_c downto ctrl_uart_pmode0_c); data_o(ctrl_uart_prsc2_c downto ctrl_uart_prsc0_c) <= ctrl(ctrl_uart_prsc2_c downto ctrl_uart_prsc0_c); data_o(ctrl_uart_en_c) <= ctrl(ctrl_uart_en_c); data_o(ctrl_uart_rx_irq_c) <= ctrl(ctrl_uart_rx_irq_c); data_o(ctrl_uart_tx_irq_c) <= ctrl(ctrl_uart_tx_irq_c); data_o(ctrl_uart_tx_busy_c) <= uart_tx.busy; else -- uart_rtx_addr_c data_o(data_rx_avail_c) <= uart_rx.avail(0); data_o(data_rx_overr_c) <= uart_rx.avail(0) and uart_rx.avail(1); data_o(data_rx_ferr_c) <= uart_rx.ferr; data_o(data_rx_perr_c) <= uart_rx.perr; data_o(07 downto 0) <= uart_rx.data; end if; end if; end if; end process rw_access; -- number of bits to be sampled -- -- if parity flag is ENABLED: 11 bit (1 start bit + 8 data bits + 1 parity bit + 1 stop bit) -- if parity flag is DISABLED: 10 bit (1 start bit + 8 data bits + 1 stop bit) num_bits <= "1011" when (ctrl(ctrl_uart_pmode1_c) = '1') else "1010"; -- Clock Selection ------------------------------------------------------------------------ -- ------------------------------------------------------------------------------------------- -- clock enable -- clkgen_en_o <= ctrl(ctrl_uart_en_c); -- uart clock select -- uart_clk <= clkgen_i(to_integer(unsigned(ctrl(ctrl_uart_prsc2_c downto ctrl_uart_prsc0_c)))); -- UART Transmitter ----------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- uart_tx_unit: process(clk_i) begin if rising_edge(clk_i) then -- serial engine -- uart_tx.done <= '0'; if (uart_tx.busy = '0') or (ctrl(ctrl_uart_en_c) = '0') or (ctrl(ctrl_uart_sim_en_c) = '1') then -- idle or disabled or in SIM mode uart_tx.busy <= '0'; uart_tx.baud_cnt <= ctrl(ctrl_uart_baud11_c downto ctrl_uart_baud00_c); uart_tx.bitcnt <= num_bits; uart_tx.sreg(0) <= '1'; if (wr_en = '1') and (ctrl(ctrl_uart_en_c) = '1') and (addr = uart_rtx_addr_c) and (ctrl(ctrl_uart_sim_en_c) = '0') then -- write trigger and not in SIM mode if (ctrl(ctrl_uart_pmode1_c) = '1') then -- add parity flag uart_tx.sreg <= '1' & (xor_all_f(data_i(7 downto 0)) xor ctrl(ctrl_uart_pmode0_c)) & data_i(7 downto 0) & '0'; -- stopbit & parity bit & data & startbit else uart_tx.sreg <= '1' & '1' & data_i(7 downto 0) & '0'; -- (dummy fill-bit &) stopbit & data & startbit end if; uart_tx.busy <= '1'; end if; elsif (uart_clk = '1') then if (uart_tx.baud_cnt = x"000") then uart_tx.baud_cnt <= ctrl(ctrl_uart_baud11_c downto ctrl_uart_baud00_c); uart_tx.bitcnt <= std_ulogic_vector(unsigned(uart_tx.bitcnt) - 1); uart_tx.sreg <= '1' & uart_tx.sreg(uart_tx.sreg'left downto 1); else uart_tx.baud_cnt <= std_ulogic_vector(unsigned(uart_tx.baud_cnt) - 1); end if; if (uart_tx.bitcnt = "0000") then uart_tx.busy <= '0'; -- done uart_tx.done <= '1'; end if; end if; -- transmitter output -- uart_txd_o <= uart_tx.sreg(0); end if; end process uart_tx_unit; -- UART Receiver -------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- uart_rx_unit: process(clk_i) begin if rising_edge(clk_i) then -- input synchronizer -- uart_rx.sync <= uart_rxd_i & uart_rx.sync(4 downto 1); -- serial engine -- if (uart_rx.busy = '0') or (ctrl(ctrl_uart_en_c) = '0') then -- idle or disabled uart_rx.busy <= '0'; uart_rx.baud_cnt <= '0' & ctrl(ctrl_uart_baud11_c downto ctrl_uart_baud01_c); -- half baud delay at the beginning to sample in the middle of each bit uart_rx.bitcnt <= num_bits; if (ctrl(ctrl_uart_en_c) = '0') then -- to ensure defined state when reading uart_rx.perr <= '0'; uart_rx.ferr <= '0'; uart_rx.data <= (others => '0'); elsif (uart_rx.sync(2 downto 0) = "001") then -- start bit? (falling edge) uart_rx.busy <= '1'; end if; elsif (uart_clk = '1') then if (uart_rx.baud_cnt = x"000") then uart_rx.baud_cnt <= ctrl(ctrl_uart_baud11_c downto ctrl_uart_baud00_c); uart_rx.bitcnt <= std_ulogic_vector(unsigned(uart_rx.bitcnt) - 1); uart_rx.sreg <= uart_rx.sync(0) & uart_rx.sreg(uart_rx.sreg'left downto 1); else uart_rx.baud_cnt <= std_ulogic_vector(unsigned(uart_rx.baud_cnt) - 1); end if; if (uart_rx.bitcnt = "0000") then uart_rx.busy <= '0'; -- done uart_rx.perr <= ctrl(ctrl_uart_pmode1_c) and (xor_all_f(uart_rx.sreg(8 downto 0)) xor ctrl(ctrl_uart_pmode0_c)); uart_rx.ferr <= not uart_rx.sreg(9); -- check stop bit (error if not set) if (ctrl(ctrl_uart_pmode1_c) = '1') then -- add parity flag uart_rx.data <= uart_rx.sreg(7 downto 0); else uart_rx.data <= uart_rx.sreg(8 downto 1); end if; end if; end if; -- RX available flag -- uart_rx.busy_ff <= uart_rx.busy; if (ctrl(ctrl_uart_en_c) = '0') or (((uart_rx.avail(0) = '1') or (uart_rx.avail(1) = '1')) and (rd_en = '1') and (addr = uart_rtx_addr_c)) then -- off/RX read access uart_rx.avail <= "00"; elsif (uart_rx.busy_ff = '1') and (uart_rx.busy = '0') then -- RX done uart_rx.avail <= uart_rx.avail(0) & '1'; end if; end if; end process uart_rx_unit; -- Interrupt ------------------------------------------------------------------------------ -- ------------------------------------------------------------------------------------------- -- UART Rx data available [OR] UART Tx complete uart_irq_o <= (uart_rx.busy_ff and (not uart_rx.busy) and ctrl(ctrl_uart_rx_irq_c)) or (uart_tx.done and ctrl(ctrl_uart_tx_irq_c)); -- SIMULATION Output ---------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- sim_output: process(clk_i) -- for SIMULATION ONLY! file file_devnull_text_out : text open write_mode is "neorv32.uart.sim_mode.text.out"; file file_devnull_data_out : text open write_mode is "neorv32.uart.sim_mode.data.out"; variable char_v : integer; variable line_screen_v : line; -- we need several line variables here since "writeline" seems to flush the source variable variable line_text_v : line; variable line_data_v : line; begin if rising_edge(clk_i) then if (ctrl(ctrl_uart_en_c) = '1') and (ctrl(ctrl_uart_sim_en_c) = '1') then -- UART enabled and simulation output selected? if (wr_en = '1') and (addr = uart_rtx_addr_c) then -- write access to tx register -- print lowest byte to ASCII char -- char_v := to_integer(unsigned(data_i(7 downto 0))); if (char_v >= 128) then -- out of range? char_v := 0; end if; if (char_v /= 10) and (char_v /= 13) then -- skip line breaks - they are issued via "writeline" if (sim_screen_output_en_c = true) then write(line_screen_v, character'val(char_v)); end if; if (sim_text_output_en_c = true) then write(line_text_v, character'val(char_v)); end if; end if; if (char_v = 10) then -- line break: write to screen and text file if (sim_screen_output_en_c = true) then writeline(output, line_screen_v); end if; if (sim_text_output_en_c = true) then writeline(file_devnull_text_out, line_text_v); end if; end if; -- dump raw data as 8 hex char text to file -- if (sim_data_output_en_c = true) then for x in 7 downto 0 loop write(line_data_v, to_hexchar_f(data_i(3+x*4 downto 0+x*4))); -- write in hex form end loop; -- x writeline(file_devnull_data_out, line_data_v); end if; end if; end if; end if; end process sim_output; end neorv32_uart_rtl;
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