--- Quote Start ---
assume input x is 16 bits signed
y_out is 16 bits signed
coeffs 16 bits signed
then you can either use integer computation or signed.
to simplify example, let us assume we can truncate y_int below without check,
I also assume a coeff of say 2 means 2 in terms of gain.
This code is untested but should give you an idea.
signal y1 : signed(32 downto 0) := (others => '0');
signal y2 : signed(33 downto 0) := (others => '0');
signal y_int : signed(34 downto 0) := (others => '0');
constant b0 : signed(15 downto 0) := x"0001";
constant b1 : signed(15 downto 0) := x"0002";
constant b2 : signed(15 downto 0) := x"0003";
constant a1 : signed(15 downto 0) := x"0002";
constant a2 : signed(15 downto 0) := x"0001";
begin
process
begin
wait until clk = '1';
y1 <= x*b2 + y_int(15 downto 0)*a2; -- 16*16 + 16*16cbits, needs 33 bits
y2 <= x*b1 + y_int(15 downto 0)*a1 + y1; -- 16*16 + 16*16 + 33bits, needs 34 bits
end process;
y_int <= x*b0 + y2; -- 16 * 16 + 34 bits, requires 35 bits
y <= y_int(15 downto 0);
--- Quote End ---
Ok. thank you for your response..
in your code there isn't extension of sign.. so when compile there are some errors.. due to different dimension of register...
so i put they of the same length ignoring for this time the correct length of the registers..
do you know some function that extent the sign automatically?
I simulate this example of qsim and this is correct.. thank you!:o
i show this on the file sim_solution.pdf with coeff b0=1 b1=2 b3=3 a1=2 a2=1
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