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Sim8051

A simple simulator for the 8051 architecture. Includes a disassembler and a simple assembly editor (+assembler) for a more streamlined workflow.

Screenshot of the simulator user interface

Head to the releases section to download the application or build it using the instructions below. Some simple example programs can be found in the examples directory. Please be aware that not every instruction has been extensively tested, so expect bugs.

Feel free to open an issue, if you find a bug or have other suggestions/ideas or questions.

Why?

I need a simulator for my little compiler project and didn't find a simple one that compiles on linux, so I thought it would make sense to "quickly" write my own.

Features

  • Simulate the microcontroller with its whole ISA.
  • Load programs from Intel hex files.
  • Timers.
  • Interrupts.
  • External ram.
  • Assembly view with decoded instructions and live-update of register content.
  • Ste-by-step execution and breakpoints (address and instruction based).
  • Assembly editor with integrated assembler that allows an easier workflow.
  • Simple decimal to hexadecimal converter (also vice versa).
  • Flexible GUI: dock or hide windows according to your preferences.

Usage notes

  • GUI docking: I recommend to create a proper layout by moving the sub-windows to the window edges.
  • The simulator is designed following the documentation in the "sources" section below.
  • Vague syntax specification for the integrated assembler can be found in Encoding.hpp. Available mnemonics can be found in keil's documentation (see sources section).
  • A few keyboard shortcuts are supported: Space (single step), R (reset MCU), CTRL+Enter while editing (save & compile), P (run/pause), L (reload all files and compile).
  • Breakpoints can be set by clicking on the left column in assembly view. You can also change the "break instruction".
  • The simulation does not mirror the hardware one-to-one. Some features like interrupts might trigger one cycle too late or ports may behave differently.
  • Labels must contain at least one non-hexadecimal character to be usable.
  • Labels can be used with any jump instructions and instruction 0x90 (mov dptr, <value/label>)

Dependencies

Install them with a package manager like "pacman" or follow the instructions on their website.

Building

This project uses cmake as build system.

SFML ist the only dependency which must be installed manually, the rest is included in the building instructions.

Linux

mkdir deps && cd deps
git clone https://github.com/ocornut/imgui
git clone https://github.com/eliasdaler/imgui-sfml
git -C imgui checkout docking # only necessary until docking branch is merged
cat imgui-sfml/imconfig-SFML.h >> imgui/imconfig.h
cd ..

mkdir build && cd build
cmake ..
make

Windows

mkdir deps && cd deps
git clone https://github.com/ocornut/imgui
git clone https://github.com/eliasdaler/imgui-sfml
git -C imgui checkout docking # only necessary until docking branch is merged

Copy imgui-sfml/imconfig-SFML.h to imgui/imconfig.h. The following assumes you have downloaded SFML into deps/sfml/SFML-2.5.1. If not, update the paths accordingly.

mkdir build && cd build
cmake .. -DSFML_DIR="deps/sfml/SFML-2.5.1/lib/cmake/SFML"
cmake --build . -j 8

If the build fails with missing include paths or .lib files, try to add -DSFML_INCLUDE_DIR="deps/sfml/SFML-2.5.1/include" -DSFML_LIB_DIR="deps/sfml/SFML-2.5.1/lib" to the cmake command.

Features that might be added some day

  • Serial port/UART
  • A/D converter
  • Models that can be connected to the ports and played around with.
  • Inline editing of SFR registers and memory while the simulator is running.
  • Support for more assembly features (like variables, including other files, "meta" mnemonics).
  • Memory breakpoints

Other notes

In theory you can use this code in your own project by just including Processor.hpp/.cpp (+stdafx.hpp) and you'll have a full simulator at your service. The "Processor" and "Encoding+Processor" modules are designed to be independent of "main", which mostly implements gui stuff. The only thing that needs to be provided is a generic "void log( const std::string & )" function for logging (see stdafx.hpp).

Sources