Skip to content

Follow up on my 8bit breadboard computer emulator, written in C++

License

Notifications You must be signed in to change notification settings

minMelody/Breadboard8

Repository files navigation

Follow up on my Breadboard8mini 8bit cpu emulator

This is an in-depth emulator of Ben Eater's 8 bit breadboard computer down to the micro instructions.

Build the project by running make, this creates a 'bb8' & 'eas' executables using g++, as well as the ROM image making use of numpy.

Run the emulator using ./bb8.exe <program file> <clock speed> [(optional)rom file]. It loads 'rom.out' by default.

Editing the microcode

The makerom python script is based on Ben Eater's arduino EEPROM programmer. Edit the template to add instructions.
When changing the micro-instruction definitions make sure to edit both the python script and 'src/include/microcode.h'.

Running python3 makerom.py outputs the rom image in 'rom.out', unless a different file is specified.

Writing your own program

See the readme file for assembler syntax. Run ./eas.exe <source code> [(optional)output path] to assemble your code. If no output path is specified a a.out file will be created.

Test program

When the microcode contains no jump if carry, shiftleft.out outputs all zeros once a value greater than 128 is reached:

example of conditional jump not implemented

Meanwhile a working jump if carry will execute in a loop:

example of working jump carry