Arithmetic Circuits
Arithmetic circuits can perform seven different arithmetic operations using a single composite circuit.
It uses a full adder (FA) to perform these operations. A multiplexer (MUX) is used to provide different inputs to the circuit in order to obtain different arithmetic operations as outputs.
4-bit Arithmetic Circuit :
Consider the following 4-bit Arithmetic circuit with inputs A and B. It can perform seven different arithmetic operations by varying the inputs of the multiplexer and the carry (C0).
Truth Table for the above Arithmetic Circuit :
S0 | S1 | C0 | MUX Output | Full Adder Output |
---|---|---|---|---|
0 |
0 |
0 |
B |
A + B |
0 |
0 |
1 |
B |
A + B + 1 |
0 |
1 |
0 |
B’ |
A + B’ |
0 |
1 |
1 |
B’ |
A + B’ + 1 = A – B |
1 |
0 |
0 |
0 |
A |
1 |
0 |
1 |
0 |
A + 1 |
1 |
1 |
0 |
1 |
A – 1 |
1 |
1 |
1 |
1 |
A – 1 + 1 = A |
Hence, the different operations for the inputs A and B are –
- A + B (adder)
- A + B + 1
- A + B’
- A – B (subtracter)
- A
- A + 1 (incrementer)
- A – 1 (decrementer)