Honored ContributorI have 3 numbers x, y, z to be added together, each with the format of s1.14. Then the sum will be in the format of s3.14. How to make judgement on whether or not there is an overflow? If it is judged based on the first 3 MSB and they are ALL either zeros or ones, is there is no overflow? why? Does the overflow in the middle cares (e.g. I have more than 3 addition)?
Honored Contributorthe rule is :
For an N bit number N + N = N+1 bits required. So N + N + N requires N+2 bits. Which is what you have, hence it will never overflow.Honored ContributorSum is just an intermediate variable for the calculation, and the final output has the same number of bits as input. Besides, there is also an output (a flag) indicating whether there is an overflow in the final result. Then, how to make a judgement on whether or not there is an overflow, and why?
Honored Contributor
if data_int(19 downto 15) = "00000" or data_int(19 downto 15) = "11111" then
dout <= data_int(15 downto 0);
clip <= '0';
elsif if data_int(19) = '0' then
dout <= 32767;
clip <= '1';
else
dout <= -32767;
clip <= '1';
end if;
If the final result doesn't have an overflow, does an overflow in the middle of the calculation matters?
Honored Contributor
