Lab 5 of 15 · rank 04

Full adder

Inputs A, B, Cin. Outputs S, Cout. Three-bit addition.

Learn first

A full adder adds three bits: A, B and a carry coming in from the column to the right.

When you add long numbers, each column takes a carry from the previous one. A full adder handles that: it adds A, B and Cin, and gives a sum S and a carry out Cout.

It's two half adders chained: the first adds A and B, the second adds that sum to Cin. Cout is 1 if either half adder carried.

Try this

Half adder #1 on A and B gives S1 and C1. Half adder #2 on S1 and Cin gives S (the final sum) and C2. Cout = C1 OR C2 (OR is a NAND fed by two NOTs — or use the HA and OR cells from the library; they compile to NAND for you).

1
Build itPorts named A, B, Cin and S, Cout
2
Pass the truth table8 rows checked
3
Etch it (optional)a verified die in your project

⊼

Cellsclick one, then click the canvas

Build your die

Turn logic into a permanent, verifiable part.

NAND used0 / par 9

LATCH used0 / par 0

Pick a cell on the left, click to place it · drag from an output pin to an input pin to wire · click a wire to remove it · click a cell to rename it

→ Y=0

What it should do

A B CinS Cout

0 0 00 0

0 0 11 0

0 1 01 0

0 1 10 1

1 0 01 0

1 0 10 1

1 1 00 1

1 1 11 1

Stuck?

Two half adders plus an OR, or the FA macro.

Par is 9 NAND. Using more still passes here. To etch it as a verified die that mines, keep it within 18 NAND-equivalent (a LATCH counts 2): the verifier refuses bigger designs, so padding can't buy mining weight.

Etch it as a die (optional)

Turn this circuit into a verified die you own. It burns 0 NAND. Get materials at the Foundry.

connect a wallet to pick a project