Full Adder With Only XOR and NAND Gates

[mPierce]

I am trying to design a full adder (just 1 bit) using only 4 XOR gates and 4 NAND gates (in other words, the 7486 and 7400 ICs). I am basing my design off this diagram: . I just cant seem to figure out how to replace the OR gate with anything other than 3 NAND gates, which doesn't leave enough to replace the AND gates. Any help would be greatly appreciated.

 

[mishrashashi]

Only 3 NAND gates can replace the AND and OR gates in logic circuit.



for further reading http://www.kpsec.freeuk.com/gates.htm

 

[mPierce]

Ahh, I see. So you can make any two level AND-OR circuit into a two level NAND-NAND circuit?

 

[mishrashashi]

any gates can be represent by universal gates NAND & NOR. Follow Demorgan's Laws to change the logic of gates.