ijmacd / simple-vm

Simple VM

This is a very simple implementation of a computer with the SAP-1 (Simple As Possible) architecture fromDigital Computer Electronics by Albert Paul Malvino.

The direct influence was of course Ben Eater's excellent youtube series building this 8-bit computer on breadboards.

I started this project for two reasons. Firstly, I didn't want to foot the bill for all those breadboards. Secondly, I wanted to learn the C progrmmaing language and the Windows Console API.

Capabilities

The computer currently has 9 machine instructions defined by Ben. These are NOP, LDA, ADD, SUB, STA, LDI, JMP, OPT and HLT. (OPT should really be OUT but for compiler reasons I had to use a different macro name.)

Currently pre-compiled into the binary are three sample programs:

• 14 + 28
• Multiples of 3
• Fibonacci Generator

Preview

Here's a screenshot demonstrating the program running.

The computer can be controlled via the keyboard and can be made to step through micro-instructions one-by-one.

Usage

vm [program_file]

The VM can run a binary file of machine instructions provided on the command line. See http://github.com/IJMacD/simple-assembler for an assembler to create the binary file.

If a program file is not provided the three built-in programs can be switched with the number keys.

Components

• A Register
• B Register
• Clock
• Instruction Register
• Program Counter
• RAM
  • Address
  • Contents
• ALU
• Output
• Bus Indicator
• Control
• Microcode EEPROM