Design of a 12-bit CPU with Basic Instructions

A Central Processing Unit (CPU) is the core component of a computer responsible for executing instructions. It performs arithmetic, logical, and control operations. Modern CPUs are integrated as microprocessors and may include multiple cores and peripheral components.

The CPU mainly consists of:

• Arithmetic Logic Unit (ALU): Performs arithmetic and logical operations
• Control Unit (CU): Fetches, decodes, and executes instructions

Registers

Registers are fast storage elements used inside the CPU:

• Instruction Register – stores current instruction
• Data Register – stores intermediate data

Memory Types

• Registers – fastest access
• Main Memory – temporary storage
• Secondary Storage – long-term storage

Main memory includes:

• RAM (Random Access Memory)
• ROM (Read Only Memory)

Instruction Sets

• CISC – Large instruction set
• RISC – Simplified instruction set for faster execution

Processing Types

• Serial Processing – one instruction at a time
• Parallel Processing – multiple instructions simultaneously

CPU Components & Interfaces

Fig.1: ALU Interface

Fig.2: ALU Function Table

Fig.3: Comparator Interface

Fig.4: Comparator Operation Table

Fig.5: Control Symbol

Fig.6: Register Symbol

Fig.7: Register Array Symbol

Fig.8: Shift Symbol

Fig.9: Shift Operations

Fig.10: Rotate Operations

Fig.11: Tri-register Symbol

CPU Block Diagram

Fig.12: Block Diagram of CPU

Observations & Data

Write and simulate the VHDL program to generate the RTL schematic and test bench waveform.

Procedure

Follow Xilinx ISE procedure for coding, simulation, and synthesis.

Conclusion

The 12-bit CPU was successfully implemented using VHDL. Simulation results confirmed correct execution of instructions and proper CPU functionality.