Basic-Computer

Mano Machine is a 16 Bit computer provided in the books by Morris Mano, which is able to execute programs like Fibonacci, Factorial, and Guess the Number Game. This repository is an implementation of Digital Logic and Circuit Design (COC2072), Digital Design & Simulation Lab (COC2922) and Computer Architecture (COC2082).

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• Decoded Instructions
• Books:
  • Computer System Architecture - M. Morris Mano
  • Digital Logic and Computer Design - M. Morris Mano

• Note: For looped circuits $(Q = f(Q))$, the sim may not be able to find the correct state, hence RESET pin is used to make initial Q as 0 - similar to setting a base case for recursion.
• Logism provides features like getting truth-table, running txt-tests, etc.
• Particulars about the version of Logisim used:
  • Product: Logisim-evolution v4.0.0
  • Runs on: Java HotSpot(TM) 64-Bit Server VM v21.0.4
  • Compiled: 2025-09-07T09:17:48+0200
  • Build ID: main/00b4b30e
  • Built on: Java HotSpot(TM) 64-Bit Server VM v21.0.4
• We may create Memory from scratch as well, but logisim allows us to load programs using Hex files.
• This repo was made such that everything feels very accessible, however logisim doesn't allow a library to be used if it was used in an already imported library. So if you are trying to re-create this probably should make everything in a single file with different circuits. Or forcefully import by writing the import statement in the .circ file.
• Pin order in logisim of the imported circuit depends on the build circuit.
• This project can be later extended to make the processor for Apple 1.
• If you find any issues, inconsistencies in notation, some logical flaw, or anything worth mentioning, please let me know. Pull requests are always welcomed.
• CLR is Synchronous, while the reset pin is Asynchronous.
• Computer Specifics: Von Neumann Architecture, Accumulator-Based (Leaning toward CISC), Hardwired Control Unit, Isolated I/O, Fixed-Length Instructions, 4K Words (8KB RAM), SISD (Single Instruction Single Data), all registers are falling-edge triggering.

How to Run

1. Ensure you have Logisim-evolution v4.0.0+ installed.
2. Clone this repo.
3. Open src/04-datapath/BasicComputer.circ.
4. To run a program: Right-click the RAM component -> Load Image -> Select your .hex file.
5. Press Ctrl + K to start the execution.

Structure:

.
├── Banner.png
├── README.md
├── shortcuts.svg
├── src
│   ├── 00-Simple Circuits
│   │   ├── 16Bit_Adder.circ
│   │   ├── 16Bit_Full_Adder.circ
│   │   ├── 16BitMux4x1.circ
│   │   ├── 4Bit_Adder_Carry_Look_Ahead.circ
│   │   ├── 4Bit_Adder_Ripple.circ
│   │   ├── 4Bit_Counter.circ
│   │   ├── Binary_Ripple_Counter_JK.circ
│   │   ├── Clocked_RS_Flip_Flop.circ
│   │   ├── Counter42513.circ
│   │   ├── D_Flip_Flop.circ
│   │   ├── Decoders.circ
│   │   ├── FinalPractical.circ
│   │   ├── Full_Adder.circ
│   │   ├── Half_Adder.circ
│   │   ├── JK_Flip_Flop.circ
│   │   ├── Master_Slave_JK_Flip_Flop.circ
│   │   ├── Memory_Cell.circ
│   │   ├── Mux2x1.circ
│   │   ├── Mux4x1.circ
│   │   ├── Mux8x1.circ
│   │   ├── Registers.circ
│   │   ├── SR_Flip_Flop.circ
│   │   └── T_Flip_Flop.circ
│   ├── 01-ALSU
│   │   ├── ALSU_Test.txt
│   │   ├── ALSU.circ
│   │   ├── ALSU.png
│   │   ├── Arithmetic_Unit.circ
│   │   ├── Arithmetic_Unit.png
│   │   ├── Logic_Unit.circ
│   │   └── Logic_Unit.png
│   ├── 02-Memory
│   │   ├── Memory_Cell.png
│   │   └── Memory.png
│   ├── 03-Control-Unit
│   │   ├── AC.circ
│   │   ├── ALU_Control.circ
│   │   ├── AR.circ
│   │   ├── Control Functions and Microoperations.png
│   │   ├── Control_Unit_Test.txt
│   │   ├── Control_Unit.circ
│   │   ├── Control_Unit.png
│   │   ├── DR.circ
│   │   ├── E.circ
│   │   ├── EnableFFs.circ
│   │   ├── IO.circ
│   │   ├── IR.circ
│   │   ├── Mem.circ
│   │   ├── PC.circ
│   │   ├── SC.circ
│   │   └── TR.circ
│   ├── 04-Datapath
│   │   ├── BasicComputer.circ
│   │   ├── BasicComputer.png
│   │   ├── Circuits Associated with AC.png
│   │   ├── Full Computer Operation.png
│   │   ├── IEN.png
│   │   ├── Interrupt Cycle.png
│   │   ├── Registers.circ
│   │   └── Registers.png
│   └── Programs
│       ├── assembler.py
│       ├── Factorial.asm
│       ├── Factorial.hex
│       ├── Factorial.mov
│       ├── Fibonacci.asm
│       ├── Fibonacci.hex
│       ├── Fibonacci.mov
│       ├── GuessGame.asm
│       ├── GuessGame.hex
│       ├── GuessGame.mov
│       ├── Sum Direct Memory.asm
│       ├── Sum Direct Memory.hex
│       └── Sum Direct Memory.mov
└── University
    ├── Computer Architecture
    │   ├── Architecture(Full content from Unit 1 to 4).pdf
    │   ├── CA_Complete.pdf
    │   └── Computer Architecture.pdf
    ├── Digital Logic and System Design
    │   ├── Unit I.pdf
    │   ├── Unit II.pdf
    │   ├── Unit III.pdf
    │   └── Unit IV.pdf
    └── Syllabus.pdf

11 directories, 80 files

Assembler:

1. Write your code: Save your assembly program as a plain text file (e.g., program.asm).

/ A simple program to add two numbers
ORG 10
START,  LDA NUM1   / Load first number into AC
        ADD NUM2   / Add second number to AC
        STA RESULT / Store the sum
        HLT        / Halt execution
NUM1,   DEC 25     / Store decimal 25
NUM2,   DEC -5     / Store decimal -5
RESULT, HEX 0      / Room for the result
END

2. Assemble the code: Run the python tool from your command line:

python assembler.py program.asm

3. Output: This creates program.hex. It automatically starts with v2.0 raw and pre-fills unmapped addresses up to your code segment with 0000, matching exactly what Logisim expects.
4. Load into Logisim: Right-click the RAM component in Logisim, choose Load Image..., select program.hex, and the instruction words will be cleanly populated in your simulation memory.