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Codiode/Problems/Combinational Logic

1-bit Full Adder

EasyLogic CircuitBuild

Every arithmetic logic unit chains this single cell to add binary numbers of any width: the carry-out of one stage becomes the carry-in of the next. The full adder takes three 1-bit inputs and produces a sum bit and a carry bit.

Sum is the XOR of all three inputs. Cout is high when two or more inputs are high.

| A | B | Cin | Sum | Cout | |-----|-----|-------|-------|--------| | 0 | 0 | 0 | 0 | 0 | | 0 | 0 | 1 | 1 | 0 | | 0 | 1 | 0 | 1 | 0 | | 0 | 1 | 1 | 0 | 1 | | 1 | 0 | 0 | 1 | 0 | | 1 | 0 | 1 | 0 | 1 | | 1 | 1 | 0 | 0 | 1 | | 1 | 1 | 1 | 1 | 1 |

Constraints

  • Combinational logic only. No flip-flops, latches, or feedback.
  • Use two-input gates only: XOR, AND, OR.
  • Reuse the first XOR result for both the Sum path and the carry path.

Topics

combinationalarithmeticadders

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