Dual-processor System with User defined simple ISA, Virtual Machine Firmware

main component:

• Arduino Mega 2560
• shared SRAM
• Processor1(ATmega328P)
• Processor2(ATmega328P)
• Arduino Nano(DDU)

parts list:

parts type	name	number
MCU	Arduino Mega 2560	1
MCU	Arduino Nano	1
MCU	Atmega328P (DIP)	2
Memory	62256 SRAM	1
IC logic	74HC245	4
IC logic	74HC595	2
IC logic	74HC04	1
IC logic	74HC125	1
IC logic	74HC165	2
Oscillator	Active Crystal 16MHz	1

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Main Component

1. BPU (Binary Programmer Unit)

The BPU is based on Arduino Mega 2560. BPU receives binary and program(load) to RAM(62256 SRAM)

2. Processor 1

Processor 1 is the first processor based on Atmega328P. It fetches and executes instructions from shared RAM, controlling data access through bus mastery.

3. Processor 2

Processor 2 is the second processor based on Atmega328P. It alternates with Processor 1 to execute instructions using shared RAM.

4. DDU (Data Display Unit)

The DDU is the data display unit, using Arduino Nano to display system status or outputs.

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How it works

  Your Computer: 
        Code -> Compile -> Binary ->  Arduino Mega 2560(BPU) 

  Arduino Mega 2560(BPU):
        Binary -> Dual328P

• Processor1,2 RESET Pin LOW (use :rst python compiler.py COM6 --monitor)
• Load Binary(8bit) in RAM (kill the Serial Monitor and python src/BPU/compiler.py <filepath> <port> <bank> <page> -b)
• Processor1,2 RESET Pin HIGH (use :run on python compiler.py COM6 --monitor)
  • -> Processor starts.
• 1. Processor 1 Acquire Bus Mastery (Processor 1 PC4 LOW; also RAM A14 on that net)
• 2. Processor 1 Read Data from 62256 RAM and processing Instruction Fetch & Execute
• 3. Processor 1 release Bus Mastery to Processor 2 (Processor 1 PC4 HIGH)
• 4. Processor 2 Read Data from 62256 RAM and processing Instruction Fetch & Execute

Fuse Bit Configuration

When you use Active Crystal(Oscillator), You need to configure the Fuse Bits to enable clock output on Processor 1 and Processor 2. If you don't have an active crystal, you can use this method(both methods need to configure fuse bits unless you use Passive Crystal.). This section explains how to configure fuse bits using only Arduino without a separate oscillator or active crystal to set up 16MHz generator and read mode.

1. Connect the Uno (A, programmer) to the PC via USB.

2. In Arduino IDE, select File > Examples > 11.ArduinoISP > ArduinoISP and upload it to the Uno to be used as programmer.

3. Connect the programmer Uno (A) and the target ex)Nano (B) as per the table below:

Programmer Uno (A)	Target (B)
D10	RESET
D11	D11
D12	D12
D13	D13
5V	5V
GND	GND

4. Connect the computer and the programmer Arduino (A) with the upload cable.

5. Windows Environment (PowerShell)

   Change to the avrdude directory:

   cd "C:\Users\user\AppData\Local\Arduino15\packages\arduino\tools\avrdude\8.0.0-arduino1\bin"

   Verify connection:

   .\avrdude.exe -C ..\etc\avrdude.conf -c avrisp -p m328p -P COM3 -b 19200 -v

   Note: Ensure the COM port (COM3) and baud rate (19200) are consistent with your setup.

   Show the FuseBit Set:

   .\avrdude.exe -C ..\etc\avrdude.conf -c avrisp -p m328p -P COM3 -b 19200 -U lfuse:r:-:h -U hfuse:r:-:h -U efuse:r:-:h

   Set 16MHz clock out:

   .\avrdude.exe -C ..\etc\avrdude.conf -c avrisp -p m328p -P COM3 -b 19200 -U lfuse:w:0xBF:m

   Set clock read mode:

   .\avrdude.exe -C ..\etc\avrdude.conf -c avrisp -p m328p -P COM3 -b 19200 -U lfuse:w:0xE0:m

   Set default:

   .\avrdude.exe -C ..\etc\avrdude.conf -c avrisp -p m328p -P COM3 -b 19200 -U lfuse:w:0xFF:m -U hfuse:w:0xDA:m -U efuse:w:0xFD:m

Usage

1. Connect the BPU to the PC.
2. Write code in your PC, compile to binary and send to BPU.
3. BPU will load the binary to RAM.
4. when you use :run to BPU, Processors will start to work.

Repository layout

Overview of this repository (Arduino sketch folders follow the usual FolderName/FolderName.ino layout):

Dual328P/
├── LICENSE
│
├── PinManual.md
├── README.md
│
├── .vscode/
│   └── settings.json
│
├── examples/
│         ├── bench/
│         │      ├── single.asm
│         │      ├── dual_0.asm
│         │      ├── dual_1.asm
│         │      └── write_single_vs_dual_bench.py
│         │
│         │             
│         ├── simple_examples/
│         │       ├── test1.asm
│         │       ├── test1.bas
│         │       ├── test2.asm
│         │       └── test2.bas
│         │
│         └── upload_test/
│                 ├── bench32K.asm
│                 ├── bench16K.asm
│                 └── write_bench.py
│ 
│
├── modifiedISP/
│   └── modifiedISP.ino
│
└── src/
      ├── BPU/
      │   ├── compiler.py
      │   ├── BPUmega/
      │   │   └── BPUmega.ino
      │   └── BPUnano/
      │       └── BPUnano.ino
      │
      ├── DDU/
      │   ├── DDU128x64/
      │   │   └── DDU128x64.ino
      │   └── DDU16x2/
      │       └── DDU16x2.ino
      │
      ├── SMU/
      │   ├── SMUeditor.py
      │   ├── SMUmega/
      │   │   └── SMUmega.ino
      │   └── SMUnano/
      │       └── SMUnano.ino
      │
      └── VMF/
          ├── proc1VMF/
          │   └── proc1VMF.ino
          └── proc2VMF/
              └── proc2VMF.ino

License

This project is under the GNU General Public License v3.0 license. See the LICENSE file for details.

• Third-Party Credits: Modified ArduinoISP: This project includes a modified version of the ArduinoISP sketch.

  Original Author: Copyright (c) 2008-2011 Randall Bohn (BSD License).

  Modifications: include 8MHz clock output on D9.

  The original copyright notices are preserved in the source code as per the BSD license requirements.