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# Connecting a 4-bit adder to a 1-bit adder

Posted on 2004-03-21

How do you connect a 1-bit full adder (designed with 9 NAND gates) to a 7483 (4-bit adder)?

I'm having problems with it working 100 percent.

1. Built the 1-bit adder (A,B,Cin); (S,Cout) , tested with the truth table; worked flawlessly.

2. Connected the 7483, making the 1-bit adder the higher-order bit. I grounded the Cin of the 7483, connected the Cout to the Cin of the 1-bit adder, connected the all Sums to leds, and A&B's to switches.

Some sums are incorrect:

(10011)+(10111) does not = 1 01010

or

(11111)+(11111) does not = 1 11110

What could I do to make this 5-bit adder work?