Overflow detector

[Lilmiss]

I am designing a BCD adder must be capable of adding two six-digit BCD
numbers to produce a six-digit sum. In essence, the adder should work as
both an adder and a subtractor (taking into account negative numbers).
What I need to know is how to code the one bit overflow output signal that
would be 1 if the addition results in an overflow (a magnitude that is too
big to be represented with 6 BCD digits) and 0 otherwise.

 

[Ralf Hildebrandt]

I am designing a BCD adder ... ....
What I need to know is how to code the one bit overflow output signal that
would be 1 if the addition results in an overflow (a magnitude that is too
big to be represented with 6 BCD digits) and 0 otherwise.

If I do not miss something, the final carry-out should be the same as
the carry-out between every BCD-digit (4-bit binary group).
http://www2.ele.ufes.br/~ailson/digital2/cld/chapter5/chapter05.doc4.html

Ralf