I have two options for adding 9 to the BCD number.
The first way I tried is as follows:
What I did is if we have 4-bit digit T as abcd:
1001 (~ 9) - abcd (in BCD) = 1001 + (2's complement of abcd) = 9's complement
the has chart implementation.
The next way is as follows:
in which I showed a truth table with a 4-bit point T (BCD abcd) as the input and a nine's complement of T as the output, I can also use the circuit with K-map.
My question is whether these paths are correct for nine supplements or not.