Subversion Repositories all_digital_fm_receiver

LIBRARY ieee;

USE ieee.std_logic_1164.all;

USE IEEE.numeric_std.ALL;

ENTITY nco IS

-- Declarations

 port ( clk   : in  std_logic;

                        reset   : in  std_logic;

                        din                     : in    signed(11 downto 0);

                        dout    : out signed(7 downto 0)

                );

END nco ;

-- hds interface_end

ARCHITECTURE behavior OF nco IS

type vectype is array (0 to 256) of signed(7 downto 0);

-- ROM cosrom 

constant cosrom  : vectype := (

0 => "01111111",

1 => "01111111",

2 => "01111111",

3 => "01111111",

4 => "01111111",

5 => "01111111",

6 => "01111111",

7 => "01111111",

8 => "01111111",

9 => "01111111",

10 => "01111111",

11 => "01111111",

12 => "01111111",

13 => "01111111",

14 => "01111111",

15 => "01111111",

16 => "01111111",

17 => "01111111",

18 => "01111111",

19 => "01111111",

20 => "01111111",

21 => "01111111",

22 => "01111111",

23 => "01111111",

24 => "01111111",

25 => "01111110",

26 => "01111110",

27 => "01111110",

28 => "01111110",

29 => "01111110",

30 => "01111110",

31 => "01111110",

32 => "01111110",

33 => "01111101",

34 => "01111101",

35 => "01111101",

36 => "01111101",

37 => "01111101",

38 => "01111101",

39 => "01111100",

40 => "01111100",

41 => "01111100",

42 => "01111100",

43 => "01111100",

44 => "01111011",

45 => "01111011",

46 => "01111011",

47 => "01111011",

48 => "01111010",

49 => "01111010",

50 => "01111010",

51 => "01111010",

52 => "01111010",

53 => "01111001",

54 => "01111001",

55 => "01111001",

56 => "01111001",

57 => "01111000",

58 => "01111000",

59 => "01111000",

60 => "01110111",

61 => "01110111",

62 => "01110111",

63 => "01110111",

64 => "01110110",

65 => "01110110",

66 => "01110110",

67 => "01110101",

68 => "01110101",

69 => "01110101",

70 => "01110100",

71 => "01110100",

72 => "01110100",

73 => "01110011",

74 => "01110011",

75 => "01110011",

76 => "01110010",

77 => "01110010",

78 => "01110010",

79 => "01110001",

80 => "01110001",

81 => "01110001",

82 => "01110000",

83 => "01110000",

84 => "01101111",

85 => "01101111",

86 => "01101111",

87 => "01101110",

88 => "01101110",

89 => "01101101",

90 => "01101101",

91 => "01101101",

92 => "01101100",

93 => "01101100",

94 => "01101011",

95 => "01101011",

96 => "01101010",

97 => "01101010",

98 => "01101010",

99 => "01101001",

100 => "01101001",

101 => "01101000",

102 => "01101000",

103 => "01100111",

104 => "01100111",

105 => "01100110",

106 => "01100110",

107 => "01100101",

108 => "01100101",

109 => "01100100",

110 => "01100100",

111 => "01100011",

112 => "01100011",

113 => "01100010",

114 => "01100010",

115 => "01100001",

116 => "01100001",

117 => "01100000",

118 => "01100000",

119 => "01011111",

120 => "01011111",

121 => "01011110",

122 => "01011110",

123 => "01011101",

124 => "01011101",

125 => "01011100",

126 => "01011100",

127 => "01011011",

128 => "01011011",

129 => "01011010",

130 => "01011001",

131 => "01011001",

132 => "01011000",

133 => "01011000",

134 => "01010111",

135 => "01010111",

136 => "01010110",

137 => "01010101",

138 => "01010101",

139 => "01010100",

140 => "01010100",

141 => "01010011",

142 => "01010010",

143 => "01010010",

144 => "01010001",

145 => "01010001",

146 => "01010000",

147 => "01001111",

148 => "01001111",

149 => "01001110",

150 => "01001110",

151 => "01001101",

152 => "01001100",

153 => "01001100",

154 => "01001011",

155 => "01001010",

156 => "01001010",

157 => "01001001",

158 => "01001000",

159 => "01001000",

160 => "01000111",

161 => "01000111",

162 => "01000110",

163 => "01000101",

164 => "01000101",

165 => "01000100",

166 => "01000011",

167 => "01000011",

168 => "01000010",

169 => "01000001",

170 => "01000001",

171 => "01000000",

172 => "00111111",

173 => "00111110",

174 => "00111110",

175 => "00111101",

176 => "00111100",

177 => "00111100",

178 => "00111011",

179 => "00111010",

180 => "00111010",

181 => "00111001",

182 => "00111000",

183 => "00111000",

184 => "00110111",

185 => "00110110",

186 => "00110101",

187 => "00110101",

188 => "00110100",

189 => "00110011",

190 => "00110011",

191 => "00110010",

192 => "00110001",

193 => "00110000",

194 => "00110000",

195 => "00101111",

196 => "00101110",

197 => "00101101",

198 => "00101101",

199 => "00101100",

200 => "00101011",

201 => "00101010",

202 => "00101010",

203 => "00101001",

204 => "00101000",

205 => "00100111",

206 => "00100111",

207 => "00100110",

208 => "00100101",

209 => "00100100",

210 => "00100100",

211 => "00100011",

212 => "00100010",

213 => "00100001",

214 => "00100001",

215 => "00100000",

216 => "00011111",

217 => "00011110",

218 => "00011110",

219 => "00011101",

220 => "00011100",

221 => "00011011",

222 => "00011011",

223 => "00011010",

224 => "00011001",

225 => "00011000",

226 => "00011000",

227 => "00010111",

228 => "00010110",

229 => "00010101",

230 => "00010100",

231 => "00010100",

232 => "00010011",

233 => "00010010",

234 => "00010001",

235 => "00010001",

236 => "00010000",

237 => "00001111",

238 => "00001110",

239 => "00001101",

240 => "00001101",

241 => "00001100",

242 => "00001011",

243 => "00001010",

244 => "00001010",

245 => "00001001",

246 => "00001000",

247 => "00000111",

248 => "00000110",

249 => "00000110",

250 => "00000101",

251 => "00000100",

252 => "00000011",

253 => "00000010",

254 => "00000010",

255 => "00000001",

256 => "00000000");

signal dtemp  : unsigned(17 downto 0);

signal din_buf  : signed(17 downto 0);

signal dtemp1  : integer;

constant offset : unsigned(17 downto 0) := "000100000000000000";

begin

process(CLK, RESET)

begin

        if (RESET='1') then

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

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

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

                                                dtemp1 <= 0;

        elsif rising_edge(CLK) then

                        din_buf <= din(11)&din(11)&din(11)&din(11)&din(11)&din(11)&din;

                                                dtemp <= dtemp + unsigned(din_buf) + offset;

                                                dtemp1 <= to_integer(dtemp(17 downto 8));

                                                if (dtemp1 >= 0) and (dtemp1 < 257) then

                                                        dout <= cosrom(dtemp1);

                                                elsif (dtemp1 >= 257) and (dtemp1 < 513) then

                                                        dout <= -cosrom(512-dtemp1);

                                                elsif (dtemp1 >= 513) and (dtemp1 < 769) then

                                                        dout <= -cosrom(dtemp1-512);

                                                else

                                                        dout <= cosrom(1024-dtemp1);

                                                end if;

    end if;

end process;

END behavior;