LEARNING OUTCOMES

Design and implement an ALU supporting N-bit operations such as addition, subtraction, bitwise AND/OR, and shifts.

TASKS

1.   Design ALU components for basic arithmetic and logical operations.

2.   Simulate the design using a Simulation Tool.

3.   Test ALU for different bit widths (16-bit) and various operations

DESCRIPTION 

The Arithmetic Logic Unit (ALU) is a core component of a computer's CPU (Central Processing Unit). It performs many operations. The ALU works by taking input data from the CPU, performing the requested operations, and sending the results back. It plays a critical role in executing instructions in computing systems. The size of the ALU determines how much data it can process simultaneously.

16 BIT ALU REFERENCE IMAGE

The uploaded image depicts a digital circuit diagram, for a 16-bit Arithmetic Logic Unit (ALU). Here's some general information based on the structure and components in the diagram:

Key Observations:

1. Inputs:
   
   

   • Two 16-bit inputs labeled as A and B, which are typically the operands for the operations performed by the ALU.

2. Operations:
   
   

   • The circuit contains a variety of blocks for logical and arithmetic operations:

     • Adder/Subtractor: Likely implemented using a combination of XOR gates and an adder block.

     • Logical Operators: Includes AND, OR, NOT gates for bitwise operations.

     • Shifters/Rotators: May be present for shifting bits left or right.

     • Multiplexer (MUX): Combines the results of different operations and selects the output based on the opcode.

3. Opcode:
   
   

   • A control line (labelled Opcode) determines the operation the ALU will perform. This is a 4-bit line in your diagram, suggesting up to 24=162^4 = 16 operations can be encoded.

4. Outputs:
   
   

   • The final 16-bit result is produced and sent to the output labeled x32 Output.

   • Flags (carry, zero, overflow, etc.) may also be generated to indicate the status of operations.

5. Registers and Buffers:
   
   

   • There are several blocks with labels like latch or similar, likely used to store intermediate results or synchronize operations.

Functionality:

• The diagram is likely implementing a multi-functional ALU capable of:

  • Basic arithmetic (addition, subtraction).

  • Logical operations (AND, OR, XOR, NOT).

  • Bit manipulation (shifting, rotating).

  • Comparison operations (greater than, less than, equal to).

Multiplexer:

• The large multiplexer toward the right combines outputs from various operations and selects one based on the opcode.

Applications:

This type of ALU is commonly used in:

• Microprocessors to perform arithmetic and logic tasks.

• FPGA or VLSI designs for custom computing systems.

• Educational tools for understanding digital circuit design.

8 BIT  ALU REFERENCE IMAGE

Working

1.Input 

Two n-bit inputs labeled A and B are provided. 

2. Functional Unit 

Arithmetic Operations:

ADD: Adds A and B.

SUB: Subtracts B from A.

MUL: Multiplies A and B.

DIV: Divides A by B, producing both a quotient and a remainder.

logical Operations:

AND: Performs a bitwise AND between A and B.

OR: Performs a bitwise OR between A and B.

NAND: Performs a bitwise NAND between A and B.

NOR: Performs a bitwise NOR between A and B.

Bitwise Shift/Rotation Operations:

SHL (Shift Left): Shifts the bits of A left by one or more positions.

SHR (Shift Right): Shifts the bits of A right by one or more positions.

ROL (Rotate Left): Rotates the bits of A to the left.

ROR (Rotate Right): Rotates the bits of A to the right.

3.Opcode Selector 

The opcode is a 4-bit value that selects which operation the ALU should perform. Each opcode corresponds to one functional unit 

4.Multiplexer 

The multiplexer selects the output of one functional unit based on the opcode value. 

If the opcode is 0000, the ADD operation result is selected 

If the opcode is 0001, the SUB operation result is selected 

If the opcode is 0010, the MUL operation result is selected 

If the opcode is 0011, the DIV operation result is selected 

If the opcode is 0100, the AND operation result is selected 

If the opcode is 0101, the OR operation result is selected 

If the opcode is 0110, the NAND operation result is selected 

If the opcode is 0111, the NOR operation result is selected 

If the opcode is 1000, the SHL operation result is selected 

If the opcode is 1001, the SHR operation result is selected 

If the opcode is 1010, the ROL operation result is selected 

If the opcode is 1011, the ROR operation result is selected 

5.Output Selection

The output of the selected operation is displayed.