Overflow detection

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Basically:

• 2's complement overflow occurs if adding 2 similarly signed numbers results in a different sign.
  
•  To detect overflow, see if the XOR of the Couts of the 2 MSBs is 1.
  
• Overflow will never occur when adding 2 differently signed numbers.
  
• This type of overflow is different from just the Cout.
  

If we go a bit further with those flags :



With 8 bit register


I don't really understand why in the last addition the falg N is set ...

source : https://paws.kettering.edu/~jkwon/teachi...umbers.pdf