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Altera_Forum
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9 years ago

How to square a fixed point number?

Assuming I have a 16 bit fixed point number that needs to be squared, how should this be implemented? The number format is Q2.14. Squaring it shall produce a result that is 32 bits instead a...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
9 years ago

Thank you for your responses, I have been looking into this topic for a while and have a few more questions now.

First, as mentioned by FvM, since the quantity is signed and the sign bit is implicit and not counted (the MSb) the format shall become signed Q2.13. Now if I square this, the result would be 32 bits and shall be written as Q4.26? This does not look write as it does not add to 31 but adds to 30 only. What is wrong?

It is only today I have found that there are some packages for fixed point arithmatic within VHDL. However, it is not clear to me how old these are or how much support they have in synthesis so I shall have to post a new question. I have only used std_logic_1164 and did not know that there are packages created for supporting fixed point arithmatic.