Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
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...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
11 years ago

--- Quote Start ---

are you sure? try multiply 8 bits value by 8 bits value onto 16 bits result

--- Quote End ---

The multiply and divide functions in numeric_std return a result that is N+M bits long. But addition/subtraction returns a result that is as long as the largest operand.

--- Quote Start ---

why? what is the resize doing anyway?

--- Quote End ---

The resize function does 0 extension for unsigned and sign extension for signed. It extends (or shrinks) the value the specified length.