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Codiode/Problems/Arithmetic

4-bit Bus Adder

MediumLogic CircuitBuild

Datapaths move numbers as multi-bit buses, not loose wires. A 4-bit adder sums two 4-bit operands and a carry-in, producing a 4-bit sum bus and a single carry-out that signals overflow past 15.

Sum is the low 4 bits of A + B + Cin. Cout is the bit that overflows out of the top.

| A | B | Cin | Sum | Cout | |------|------|-------|-------|--------| | 5 | 3 | 0 | 8 | 0 | | 9 | 6 | 0 | 15 | 0 | | 8 | 8 | 0 | 0 | 1 | | 15 | 15 | 1 | 15 | 1 |

Constraints

  • A, B, and Sum are 4-bit buses. Cin and Cout are 1-bit.
  • Use the bus adder (BUSADD) configured to width 4. Do not unroll into single-bit full adders.
  • Cout must reflect carry out of bit 3, not a saturated value.

Topics

arithmeticaddersbuses

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