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Removed divider from dds

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This commit is contained in:
T-moe
2016-05-24 15:57:02 +02:00
parent 58120b0a85
commit 57de5f7af7
1 changed files with 11 additions and 7 deletions
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18
dds.vhd
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@@ -25,12 +25,12 @@ use work.helpers.all;
entity dds is
Generic (clk_freq: natural:= 50000000;
max_freq: natural := 100000;
adc_res: natural:=12;
acc_res: natural:=32;
phase_res: natural:=15);
freq_res: natural:=17; -- width of frequency input (log2(max_freq))
adc_res: natural:=12; -- width of the ouput signal (=adc resolution)
acc_res: natural:=32; -- width of the phase accumulator
phase_res: natural:=15); -- effective phase resolution for lookup tables
Port ( clk : in STD_LOGIC;
freq : in unsigned (16 downto 0); --log2_int(max_freq)-1
freq : in unsigned (freq_res-1 downto 0);
form : in unsigned (1 downto 0);
amp : out unsigned (adc_res-1 downto 0));
end dds;
@@ -53,8 +53,12 @@ architecture Behavioral of dds is
begin
-- m = fout*(2^n)/fclk
m <= resize(divide(shift_left(resize(freq,64),acc_res),to_unsigned(clk_freq,64)),m'length);
-- m = fout*(2^n)/fclk = fout*((2^n)*(2^k)/fclk)/(2^k) with k=ceil(log2(fclk)), n=acc_res
m <= resize( (resize(freq,64)
*
(shift_left(to_unsigned(1,64),acc_res + log2_int(clk_freq)) / clk_freq))
/to_unsigned(2**log2_int(clk_freq),64),acc_res);
idx_phase <= idx(acc_res -1 downto acc_res - phase_res);
amp_rect <= to_unsigned(0,adc_res) when idx_phase(phase_res-1)='0' else