| 1 |
2 |
jsauermann |
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
|
| 2 |
|
|
"http://www.w3.org/TR/html4/strict.dtd">
|
| 3 |
|
|
<HTML>
|
| 4 |
|
|
<HEAD>
|
| 5 |
|
|
<TITLE>html/Listing_of_uart_rx.vhd</TITLE>
|
| 6 |
|
|
<META NAME="generator" CONTENT="HTML::TextToHTML v2.46">
|
| 7 |
|
|
<LINK REL="stylesheet" TYPE="text/css" HREF="lecture.css">
|
| 8 |
|
|
</HEAD>
|
| 9 |
|
|
<BODY>
|
| 10 |
|
|
<P><table class="ttop"><th class="tpre"><a href="25_Listing_of_status_reg.vhd.html">Previous Lesson</a></th><th class="ttop"><a href="toc.html">Table of Content</a></th><th class="tnxt"><a href="27_Listing_of_uart_tx.vhd.html">Next Lesson</a></th></table>
|
| 11 |
|
|
<hr>
|
| 12 |
|
|
|
| 13 |
|
|
<H1><A NAME="section_1">26 LISTING OF uart_rx.vhd</A></H1>
|
| 14 |
|
|
|
| 15 |
|
|
<pre class="vhdl">
|
| 16 |
|
|
|
| 17 |
|
|
1 -------------------------------------------------------------------------------
|
| 18 |
|
|
2 --
|
| 19 |
|
|
3 -- Copyright (C) 2009, 2010 Dr. Juergen Sauermann
|
| 20 |
|
|
4 --
|
| 21 |
|
|
5 -- This code is free software: you can redistribute it and/or modify
|
| 22 |
|
|
6 -- it under the terms of the GNU General Public License as published by
|
| 23 |
|
|
7 -- the Free Software Foundation, either version 3 of the License, or
|
| 24 |
|
|
8 -- (at your option) any later version.
|
| 25 |
|
|
9 --
|
| 26 |
|
|
10 -- This code is distributed in the hope that it will be useful,
|
| 27 |
|
|
11 -- but WITHOUT ANY WARRANTY; without even the implied warranty of
|
| 28 |
|
|
12 -- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
| 29 |
|
|
13 -- GNU General Public License for more details.
|
| 30 |
|
|
14 --
|
| 31 |
|
|
15 -- You should have received a copy of the GNU General Public License
|
| 32 |
|
|
16 -- along with this code (see the file named COPYING).
|
| 33 |
|
|
17 -- If not, see http://www.gnu.org/licenses/.
|
| 34 |
|
|
18 --
|
| 35 |
|
|
19 -------------------------------------------------------------------------------
|
| 36 |
|
|
20 -------------------------------------------------------------------------------
|
| 37 |
|
|
21 --
|
| 38 |
|
|
22 -- Create Date: 14:22:28 11/07/2009
|
| 39 |
|
|
23 -- Design Name:
|
| 40 |
|
|
24 -- Module Name: uart_rx - Behavioral
|
| 41 |
|
|
25 -- Description: a UART receiver.
|
| 42 |
|
|
26 --
|
| 43 |
|
|
27 -------------------------------------------------------------------------------
|
| 44 |
|
|
28 --
|
| 45 |
|
|
29 library IEEE;
|
| 46 |
|
|
30 use IEEE.STD_LOGIC_1164.ALL;
|
| 47 |
|
|
31 use IEEE.STD_LOGIC_ARITH.ALL;
|
| 48 |
|
|
32 use IEEE.STD_LOGIC_UNSIGNED.ALL;
|
| 49 |
|
|
33
|
| 50 |
|
|
34 entity uart_rx is
|
| 51 |
|
|
35 PORT( I_CLK : in std_logic;
|
| 52 |
|
|
36 I_CLR : in std_logic;
|
| 53 |
|
|
37 I_CE_16 : in std_logic; -- 16 times baud rate
|
| 54 |
|
|
38 I_RX : in std_logic; -- Serial input line
|
| 55 |
|
|
39
|
| 56 |
|
|
40 Q_DATA : out std_logic_vector(7 downto 0);
|
| 57 |
|
|
41 Q_FLAG : out std_logic); -- toggle on every byte received
|
| 58 |
|
|
42 end uart_rx;
|
| 59 |
|
|
43
|
| 60 |
|
|
44 architecture Behavioral of uart_rx is
|
| 61 |
|
|
45
|
| 62 |
|
|
46 signal L_POSITION : std_logic_vector(7 downto 0); -- sample position
|
| 63 |
|
|
47 signal L_BUF : std_logic_vector(9 downto 0);
|
| 64 |
|
|
48 signal L_FLAG : std_logic;
|
| 65 |
|
|
49 signal L_SERIN : std_logic; -- double clock the input
|
| 66 |
|
|
50 signal L_SER_HOT : std_logic; -- double clock the input
|
| 67 |
|
|
51
|
| 68 |
|
|
52 begin
|
| 69 |
|
|
53
|
| 70 |
|
|
54 -- double clock the input data...
|
| 71 |
|
|
55 --
|
| 72 |
|
|
56 process(I_CLK)
|
| 73 |
|
|
57 begin
|
| 74 |
|
|
58 if (rising_edge(I_CLK)) then
|
| 75 |
|
|
59 if (I_CLR = '1') then
|
| 76 |
|
|
60 L_SERIN <= '1';
|
| 77 |
|
|
61 L_SER_HOT <= '1';
|
| 78 |
|
|
62 else
|
| 79 |
|
|
63 L_SERIN <= I_RX;
|
| 80 |
|
|
64 L_SER_HOT <= L_SERIN;
|
| 81 |
|
|
65 end if;
|
| 82 |
|
|
66 end if;
|
| 83 |
|
|
67 end process;
|
| 84 |
|
|
68
|
| 85 |
|
|
69 process(I_CLK, L_POSITION)
|
| 86 |
|
|
70 variable START_BIT : boolean;
|
| 87 |
|
|
71 variable STOP_BIT : boolean;
|
| 88 |
|
|
72 variable STOP_POS : boolean;
|
| 89 |
|
|
73
|
| 90 |
|
|
74 begin
|
| 91 |
|
|
75 START_BIT := L_POSITION(7 downto 4) = X"0";
|
| 92 |
|
|
76 STOP_BIT := L_POSITION(7 downto 4) = X"9";
|
| 93 |
|
|
77 STOP_POS := STOP_BIT and L_POSITION(3 downto 2) = "11"; -- 3/4 of stop bit
|
| 94 |
|
|
78
|
| 95 |
|
|
79 if (rising_edge(I_CLK)) then
|
| 96 |
|
|
80 if (I_CLR = '1') then
|
| 97 |
|
|
81 L_FLAG <= '0';
|
| 98 |
|
|
82 L_POSITION <= X"00"; -- idle
|
| 99 |
|
|
83 L_BUF <= "1111111111";
|
| 100 |
|
|
84 Q_DATA <= "00000000";
|
| 101 |
|
|
85 elsif (I_CE_16 = '1') then
|
| 102 |
|
|
86 if (L_POSITION = X"00") then -- uart idle
|
| 103 |
|
|
87 L_BUF <= "1111111111";
|
| 104 |
|
|
88 if (L_SER_HOT = '0') then -- start bit received
|
| 105 |
|
|
89 L_POSITION <= X"01";
|
| 106 |
|
|
90 end if;
|
| 107 |
|
|
91 else
|
| 108 |
|
|
92 L_POSITION <= L_POSITION + X"01";
|
| 109 |
|
|
93 if (L_POSITION(3 downto 0) = "0111") then -- 1/2 bit
|
| 110 |
|
|
94 L_BUF <= L_SER_HOT & L_BUF(9 downto 1); -- sample data
|
| 111 |
|
|
95 --
|
| 112 |
|
|
96 -- validate start bit
|
| 113 |
|
|
97 --
|
| 114 |
|
|
98 if (START_BIT and L_SER_HOT = '1') then -- 1/2 start bit
|
| 115 |
|
|
99 L_POSITION <= X"00";
|
| 116 |
|
|
100 end if;
|
| 117 |
|
|
101
|
| 118 |
|
|
102 if (STOP_BIT) then -- 1/2 stop bit
|
| 119 |
|
|
103 Q_DATA <= L_BUF(9 downto 2);
|
| 120 |
|
|
104 end if;
|
| 121 |
|
|
105 elsif (STOP_POS) then -- 3/4 stop bit
|
| 122 |
|
|
106 L_FLAG <= L_FLAG xor (L_BUF(9) and not L_BUF(0));
|
| 123 |
|
|
107 L_POSITION <= X"00";
|
| 124 |
|
|
108 end if;
|
| 125 |
|
|
109 end if;
|
| 126 |
|
|
110 end if;
|
| 127 |
|
|
111 end if;
|
| 128 |
|
|
112 end process;
|
| 129 |
|
|
113
|
| 130 |
|
|
114 Q_FLAG <= L_FLAG;
|
| 131 |
|
|
115
|
| 132 |
|
|
116 end Behavioral;
|
| 133 |
|
|
117
|
| 134 |
|
|
<pre class="filename">
|
| 135 |
|
|
src/uart_rx.vhd
|
| 136 |
|
|
</pre></pre>
|
| 137 |
|
|
<P>
|
| 138 |
|
|
|
| 139 |
|
|
<P><hr><BR>
|
| 140 |
|
|
<table class="ttop"><th class="tpre"><a href="25_Listing_of_status_reg.vhd.html">Previous Lesson</a></th><th class="ttop"><a href="toc.html">Table of Content</a></th><th class="tnxt"><a href="27_Listing_of_uart_tx.vhd.html">Next Lesson</a></th></table>
|
| 141 |
|
|
</BODY>
|
| 142 |
|
|
</HTML>
|
