I need to Modify my Full Adder implementation to conduct addition of two 4-bit binary numbers. The new implementation should give the summation of two numbers and any overflow carry out. How can I achieve this???

Can I use two Full Adders (one 4-bit binary numbers as input for each Full Adder) ????

  • \$\begingroup\$ Load the 2 numbers, 4 bits each, into a ParallelLoad ShiftRegister. Also have a FlipFlop to hold the CarryIN bit. Now just shift the bits, one at a ttime, into your FullAdder and wait for that new one-bit-wide sum/carry to appear (50 nanoseconds, right?). Then clock the new Sum into Serial Input of a 3rd ShiftRegister and save the new Carry in the same ole Carry Flag FF. Clock till done. \$\endgroup\$ Apr 16, 2017 at 8:30
  • \$\begingroup\$ @analogsystemsrf: I really need the Logical Circuit. And I cannot find at least a simple chance to get through it. I'm new and a Beginner of studying Computer Systems. So can you be more dramatic? Any graphical representations??? \$\endgroup\$
    – JaanuB
    Apr 16, 2017 at 8:44
  • \$\begingroup\$ Welcome to the site. Please recognise that this is not a free design house or an on-line technical encyclopedia, copied out to you on demand. People will help you take the next step if your questions shows that you've done as much as you possibly could on your own - which your post doesn't, I'm afraid. Please either revise your question showing your work and findings so far or delete it if you find Internet searches give you your answer anyway. Again, a warm welcome to you. \$\endgroup\$
    – TonyM
    Apr 16, 2017 at 10:04
  • \$\begingroup\$ If you know 1+1=0 + Carry, using XOR gates, does this help? \$\endgroup\$ Apr 16, 2017 at 10:29
  • \$\begingroup\$ Yes I know it @TonyStewart.EEsince'75 Thank you for the help \$\endgroup\$
    – JaanuB
    Apr 16, 2017 at 10:31

1 Answer 1


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If you search Digikey for older full adders TTL and CD4xxx series, you can find block diagrams.


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