Design a circuit that takes as input, a single BCD digit and generates the 9s complement. Show truth tables, K-maps, and reduced equations. Eploit "don't cares" where possible.
The 9s complement of a BCD digit can be used similarly to the way ones and twos complements of binary numbers are used preform subtraction via addition. The 9s complement of a BCD digit is simply the BCD coded result of subtracting the digit from 9. This the 9s complement of the BCD digit for 0111 (7) is 0010 (9-7 = 2).