Design a 4-2-1-8 BCD code converter to drive a seven-segment indicator. The four inputs to the converter circuit (A, B, C, and D in the figure above) represent an 8-4-2-1 binary-coded-decimal digit. Assume that only input combinations representing the digits 0 through 9 can occur as inputs so that the combinations 1010 through 1111 are dont-cares. Design your circuit using only two-, three-, and four-input NOR gates and inverters. Try to minimize the number of gates required. The variables A, B, C, and D will be available from toggle switches.

Use

Use b (not b ) for 6. Use- (not ) for 9