578 4-bit ALU
578 : 4-bit ALU
- Author: Richard Xu, Louis Barbosa, Hallie Ho, Emmy Xu, Gia Bhatia, Emily Chen
- Description: The 4-bit ALU is designed to perform basic arithmetic and logical operations on 4-bit binary numbers
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Project Datasheet: 4-Bit ALU
Overview
The 4-Bit ALU is designed to perform various arithmetic and logical operations on 4-bit binary numbers. It supports operations such as addition, subtraction, multiplication, division, and several logical operations. Additionally, it includes an encryption function that can be used to encrypt 4-bit inputs using an 8-bit key. This capstone project is from the MIT BWSI Basics of ASICs class.
How it Works
The module accepts two 4-bit binary numbers, a and b, and a 4-bit operation code (opcode) that determines the operation to be performed. The results are then output through the uo_out wire, while additional status information, such as carry out and overflow, is output through the uio_out wire. The uio_oe wire controls the enable or disable functionality for the uio_in and uio_out wires.
Operations
- ADD: Adds
aandb, producing a 4-bit result and a carry out. - SUB: Subtracts
bfroma, producing a 4-bit result and a borrow indication. - MUL: Multiplies
aandb, producing an 8-bit result. - DIV: Divides
abyb, producing a 4-bit quotient and remainder. Division by zero is handled by returning a zero result. - AND: Performs a logical AND operation on
aandb. - OR: Performs a logical OR operation on
aandb. - XOR: Performs a logical XOR operation on
aandb. - NOT: Performs a logical NOT operation on
a, withbbeing ignored. - ENC: Encrypts the inputs
aandbusing an 8-bit key derived from concatenatingaandb. The encryption function applies an XOR operation between this 8-bit concatenated value and a fixed 8-bit key. The result is an 8-bit encrypted value.
How to Test
To test this 4-bit ALU chip, set the values for a and b based on the 4-bit binary values for each, as well as the 4-bit operation code. The output can be up to 8-bits, using the uo pins along with the first 4 bidirectional pins. The uio pin 6 is used for the carry out, and the uio 7 is used for the overflow.
External hardware
N/A
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | a[0] | result[0] | opcode[0] |
| 1 | a[1] | result[1] | opcode[1] |
| 2 | a[2] | result[2] | opcode[2] |
| 3 | a[3] | result[3] | opcode[3] |
| 4 | b[0] | result[4] | |
| 5 | b[1] | result[5] | |
| 6 | b[2] | result[6] | carry_out |
| 7 | b[3] | result[7] | overflow |