Half Adder
Inputs
| Pin | Type | Description |
|---|---|---|
| A | bit | First addend |
| B | bit | Second addend |
Outputs
| Pin | Type | Description |
|---|---|---|
| Sum | bit | A XOR B |
| Carry | bit | A AND B |
How It Works
A Half Adder adds two single bits and produces a sum and a carry output.
Logic: Sum = A XOR B, Carry = A AND B.
It cannot handle a carry-in from a previous stage. For multi-bit addition, use a Full Adder, which accepts an additional Carry In input.
Truth Table
| A | B | Sum | Carry |
|---|---|---|---|
| 0 | 0 | 0 | 0 |
| 0 | 1 | 1 | 0 |
| 1 | 0 | 1 | 0 |
| 1 | 1 | 0 | 1 |
Usage
Level 6. Built from an XOR gate and an AND gate. Serves as the least significant bit stage in the 8-bit adder chain — its Carry line feeds into the next Full Adder's Carry In, while its Sum feeds the LSB of the result bus.