Carry and Overflow question. Really simple.

[DorumonSg]

Okay.

Let me get this right. A carry occurs when for example I add 2 8bits binary together and get 9 bits. The extra 1 bit is the carry right? (Means I get 1 extra bit from the original 2.)

So overflow means for example when I add 2 positive binary together, and I get a negative right? (Means the result is in the wrong sign.)

So what if a carry and overflow occurs together? Which is the overflow bit?

For example If I get the result 1011 when 1 is the carry bit and 011 is the result within range. Which is the overflow bit? 1 or 0? Is the overflow bit the carry bit? or must I take the MSB of the digit that is within ranger as the overflow bit?

Hope u understand my question?

 

[vela]

You can't just look at the result and pick out the overflow bit. You have to detect the overflow condition. This page seems to describe how to do that pretty clearly:

http://teaching.idallen.com/dat2343/00s/overflow.txt