1. To write a circuit that converts 8421 code to BCD code, simplify the output equation using Karnaugh map, draw a logic circuit using only NAND gate, and compare the truth table.

[ 3-2] 8421 BCD BCD 8421 D C B 0 0 0 A Cy Yo Y3 0 Y2 0 Y1 0 0 0 0 0 1 0 0 0 1 0 0 0 0 1 2 0 0 1 0 0 0 0 1 0 3 0 0 1 1 0 0 1 1 4 0 1 0 0 0 0 0 0 1 0 0 5 0 1 0 1 0 1 0 1 6 0 1 0 0 0 1 1 0 7 0 1 1 1 0 0 1 1 1 8 1 0 0 0 0 1 0 0 0 9 1 0 0 1 0 1 0 0 1 10 1 0 1 0 1 0 0 0 0 11 1 0 1 1 1 0 0 0 1 12. 1 1 0 0 1 0 0 1 0 13 1 1 0 1 0 0 1 1 14 1 1 1 0 0 1 0 0 0 15 1 1 1 0 1 1