-- -----------------------------------------------------------------------------
-- RXD2CHAR - RS232 TxD to ASCII character converter (RS232 receiver) --
-- -----------------------------------------------------------------------------
--
-- File : 'txd2irda.vhd'
-- Author : Lars Larsson
--
-- Date : February 16, 1999
--
-- Description : This converts a RS232 RxD signal (8n1) into an ASCII character
-- and prints it together with the character's code on the console.
-- The design is a behavioral RS232 receiver for simulation.
--
-- -----------------------------------------------------------------------------
--
-- Copyright (C) 1999 Lars Larsson, Dept. of Computer Science
-- University of Hamburg
-- Vogt-Koelln-Str. 30
-- D - 22041 Hamburg, Germany
-- larsson@informatik.uni-hamburg.de
-- http://tech-www.informatik.uni-hamburg.de/~larsson
--
-- This program is free software; you can redistribute it and/or modify it
-- under the terms of the GNU General Public License as published by the
-- Free Software Foundation; either version 2 of the License, or (at your
-- option) any later version.
--
-- This program is distributed in the hope that it will be useful, but
-- WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
-- for more details.
--
-- You should have received a copy of the GNU General Public License along
-- with this program; if not, write to the Free Software Foundation, Inc.,
-- 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
--
-- -----------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
entity rxd2char is
port(
t : in time; -- T_BAUD = 1/(baud rate)
rs232_rxd : in std_ulogic; -- RS232 RxD signal input
bin : out std_ulogic_vector (7 downto 0); -- binary code
chr : out character; -- character
strobe : out std_ulogic -- strobe signal
);
end rxd2char;
architecture simulate of rxd2char is
type char_indexed_by_integer is array (integer range 0 to 127) of character;
constant integer_to_char : char_indexed_by_integer :=
(
NUL, SOH, STX, ETX, EOT, ENQ, ACK, BEL,
BS, HT, LF, VT, FF, CR, SO, SI,
DLE, DC1, DC2, DC3, DC4, NAK, SYN, ETB,
CAN, EM, SUB, ESC, FSP, GSP, RSP, USP,
' ', '!', '"', '#', '$', '%', '&', ''',
'(', ')', '*', '+', ',', '-', '.', '/',
'0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', ':', ';', '<', '=', '>', '?',
'@', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
'X', 'Y', 'Z', '[', '\', ']', '^', '_',
'`', 'a', 'b', 'c', 'd', 'e', 'f', 'g',
'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
'p', 'q', 'r', 's', 't', 'u', 'v', 'w',
'x', 'y', 'z', '{', '|', '}', '`', DEL
);
signal irda_s : std_ulogic;
signal baud_clk_s : std_ulogic;
signal strobe_s : std_ulogic := '0';
signal shift_reg_s : std_ulogic_vector (9 downto 0) := (others=>'1');
signal byte_s : std_ulogic_vector (7 downto 0) := (others=>'0');
signal char_s : character;
function v2s( x : std_ulogic_vector ) return string is
variable s : string( x'left+1 downto 1 ) := (others => '.');
begin
for i in x'range loop
if ( x(i) = '0' ) then s(i+1) := '0';
elsif ( x(i) = '1' ) then s(i+1) := '1';
elsif ( x(i) = 'Z' ) then s(i+1) := 'Z';
elsif ( x(i) = 'U' ) then s(i+1) := 'U';
elsif ( x(i) = 'X' ) then s(i+1) := 'X';
else s(i+1) := '*';
end if;
end loop;
return s;
end;
begin
baud_p : process
begin
wait on rs232_rxd for 1 ns;
baud_clk_s <= '0'; wait for t/2;
baud_clk_s <= '1'; wait for t/2;
end process;
shift_p : process ( baud_clk_s, rs232_rxd, shift_reg_s )
begin
if (baud_clk_s'event and baud_clk_s='1') then
if (strobe_s='1') then
byte_s <= shift_reg_s(8 downto 1);
shift_reg_s <= rs232_rxd & "111111111";
else
shift_reg_s <= rs232_rxd & shift_reg_s(9 downto 1);
end if;
end if;
end process;
save_p : process ( shift_reg_s )
begin
if (shift_reg_s(9)='1' and shift_reg_s(0)='0') then
strobe_s <= '1';
else
strobe_s <= '0';
end if;
end process;
bin <= byte_s;
chr <= char_s;
strobe <= strobe_s after t;
chk_p : process (byte_s)
begin
-- char_s <= integer_to_char(conv_integer(To_StdLogicVector(byte_s)));
if (byte_s(7)='0') then
char_s <= character'val(conv_integer(To_StdLogicVector(byte_s)));
else
char_s <= '*';
end if;
end process;
assert (rising_edge(strobe_s))
report "RS232 RECEIVER SIMULATOR (rxd2char) : (" & v2s(byte_s) & ")_2 = '" & char_s & "' "
severity note;
end simulate;
-- -----------------------------------------------------------------------------
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