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Altera_Forum
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11 years ago

Simple Signed Adder is complex to understand

Hi guys, still asking beginner questions, sorry. I have this code and cant figure out what the '0' in ('0' & cin) is doing. This is what I think: Lets say we we need to do add two to negative four...
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Altera_Forum
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11 years ago

Books try teaching from basics and are many times distant from practice.

if A & B are 4 bits each then their sum needs 5 bits (it is this extra magnitude MSB that can be passed to another adder to complete the job) but all you need is:

sum <= std_logic_vector(resize(signed(A),5) + resize(signed(B ) ,5));