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