/z80

A basic z80 virtual machine written using C# (TDD). This forms the engine of a tool for teaching assembler.

Primary LanguageC#

Build status

z80

This project contains my implementation of a z80 emulator written in C#. I've been mainly using http://z80-heaven.wikidot.com/ as source for the definition of each of the instructions.

The solution has been split up into a number of projects:

  • z80vm - this is a .net standard class library containing the processor's memory, registers and implementations of each of the commands (ADD A, B etc)

  • z80Assembler - this is a .net standard class library containing

    • PARSER: this parses commands from their textual representation converts them into their hexadecimal codes
    • LOADER: stores hexadecimal commands in memory
    • COMMAND RUNNER: executes the commands stored in memory

  • z80.ide - this is a .net framework windows forms application which implements a very simple debugger.

  • z80.example - this is a .net framework console application showing how to use the APIs.

  • z80vm.Tests - xunit tests for the z80vm project.

  • z80Assembler.Tests - xunit tests for the z80Assembler project.

  • z80.BlindTests - console application for carrying out the blind testing of all instruction.s

Screen

The debugger supports the loading of scr format files as shown below:

Screen

Debugger

The debugger in action

Debugger

Example Program Loader

// Load the program
var loader = new Loader(machine);
loader.LoadCommands(@"
LD A, 10
LD B, 10
ADD A, B
HALT");

Example Program Runner

Once a program has been loaded into memory it can executed step-by-step as follows:

var commandRunner = new CommandRunner(machine);
var halted = false;
while (!halted)
{
    halted = commandRunner.RunNextCommand();
    Console.WriteLine("Press any key to run the next command");
    Console.ReadKey(true);
}

Note

We are misusing the halt statement in the line above to mean QUIT the program. It's actual meaning is halt the program until it we receive an interrupt.

Example Virtual Machine

using z80vm;
using static z80vm.op8;
using static z80vm.Value;

// Prepare the machine
var conditionValidator = new ConditionValidator();
var machine = new Machine(conditionValidator);

// Load an immediate value into a register
machine.LD(Reg8.A, Read8BitValue(100));

// Load the contents of another 8bit register into a register
machine.LD(Reg8.B, Read8BitValue(Reg8.A));

// Load the contents of a memory address specified by a 16bit register (BC) into a register
machine.LD(Reg8.A, Read8BitValue(valueAt(Reg16.BC)));

// Load the contents of a memory address specified by a 16bit register plus an offset (IX+n) into a register
machine.LD(Reg8.A, Read8BitValue(valueAt(Reg16.IX).Add(10)));

// Load the contents of a memory address (ofs) into a register
machine.LD(Reg8.A, Read8BitValue(valueAt(0xFFFF)));

// Load an immediate value into a memory address specified by a 16bit register (BC)
machine.LD(valueAt(Reg16.BC), Read8BitValue(100));

// Load the contents of a register into a memory address specified by a 16bit register (BC)
machine.LD(valueAt(Reg16.BC), Read8BitValue(Reg8.A));

// Load an immediate value into a memory address specified by a 16bit register plus an offset (IX+n)
machine.LD(valueAt(Reg16.IX).Add(10), Read8BitValue(100));

// Load the contents of a register into a memory address specified by a 16bit register plus an offset (IX+n)
machine.LD(valueAt(Reg16.IX).Add(10), Read8BitValue(Reg8.A));

// Loads a memory address with the value of a register
machine.LD(0xFFFE, Read8BitValue(Reg8.A));