8bitdev

This repo is used by cjs for development of programs in 8-bit assembly languages (for a variety of platforms) and tools to aid this development.

If you wish to discuss any of the code here, the best way to reach me is to contact 0cjs on Discord, or cjs_cynic on Telegram. You can also use the e-mail address in the commit messages, but that's more likely to get lost in the noise of all my e-mail and will always take longer to get a response.

Contents

• (Top Section)
  • Contents
  • Introduction
• File and Directory Organization
  • ASL (The Macroassembler AS) Notes
  • ASxxxx Notes
• Third-party Development Tools
  • VICE: The Versatile Commodore Emulator
  • MAME Multi-system Emulators
• Additional Third-party Tools
  • VICE: The Versatile Commodore Emulator
  • MAME Multi-system Emulators
• Additional Tool Information
  • Playing CMT (Cassette Tape) Images
  • The py65 Monitor

Introduction

This repo includes:

• A Python framework (under lib/) for running unit tests on 6502 machine code in the py65 6502 simulator. Unit tests use pytest and are in .pt files, generally with the same base name as the source file containing the code under test.
• Scripts (under tool/) for downloading and building development tools, including assemblers, binary file and disk image tools, and 8-bit PC simulators.

Run the top-level ./Test script to see everything go. Adding -C as the first flag will do a fully clean build, including re-installation of all tools, which may be necessary if the third-party tools have been updated.

This currently has been tested only under Linux (Debian 9), but is likely to work under MacOS and other Unices. It likely can be made to work under Windows as well, if there's demand; contact cjs@cynic.net if you're interested in getting support for this.

File and Directory Organization

Here is an overview of the major files and directories in this repo.

Files:

• README.md: This file.
• Test: Installs third-party tools where necessary, builds the code and runs the unit tests. (Bash.)
• [b8tool/pactivate]: When sourced in Bash (. ./pactivate) activates the Python virtual environment, building a new one (and installing the packages listed in requirements.txt, such as py65 and pytest) if necessary. You can also directly run programs in the virtual environment without separately activating it by running them from .build/virtualenv/bin/. Deactivate the virtual environment with deactivate.

Directories:

• bin/: Development tools/scripts.
• tool/: Third-party tool installation.
• lib/testmc/: Unit test library Python module.
• src/: Assembly source code, unit tests and documentation. These are generally modules used by full programs under exe/.
• exe/: "Top-level" assembly files for full executable program builds, usually just doing configuration and including code from src/. See exe/README.
• tmp/: Ignored; used to keep developer's random files out of the way.

Third-party Development Tools

Most of the development tools used for code in this repo are downloaded and built by the scripts under the tool/ directory. Tools already available in the path will be used instead; see the check_installed() functions in the setup scripts for details.

Beyond the packages checked above, you will need basic build tools as well. On Debian, apt-get install build-essential pkgconf. (You can also use the original Freedeskop.org pkg-config if you prefer.)

Assemblers:

• The Macroassembler AS is the primary assembler, and supports a wide variety of CPUs and microcontrollers.
• The ASxxxx Cross Assemblers are optionally available (see below), though little used.

Development Tools:

• retroabandon/osimg supplies ROM BIOS images for emulators and DOS disk images used as a base for building test images.
• Vince Weaver's dos33fsprogs provides tools for handling Apple II DOS 3.3 disk images and files.

Simulators and Emulators:

• The py65 6502 microprocessor simulator (source) is used to run unit tests.
• The LinApple Apple II emulator can be used to run Apple II programs.

py65 Notes

The PypI py65 has not been updated since July 2018 and is stuck at 1.1.0. That version produces warnings in modern versions of Python. One workaround until this is fixed is to use a version from GitHub:

.build/virtualenv/bin/pip install -U \
    py65@git+https://github.com/mnaberez/py65.git

This will pull the head of the main branch; to use a release branch append @<branch-name> to the URL.

ASL (The Macroassembler AS) Notes

Versions 1.42 builds 205 through at least 218 are broken for 8bitdev due to the "Symbols in Segment NOTHING" section disappearing from the map file. See b8tool.toolset.asl for more details.

ASxxxx Notes

The Linux binaries provided for ASxxxx are 32-bit, and on 64-bit systems will error out with "No such file or directory" when run unless the 32-bit dynamic linker (ld-linux.so.2) and libraries are installed.

For this reason, by default ASxxxx is not installed and used. Use ./Test -A to enable assembly and testing of code using ASxxxx. This is a persistent flag (even across fully clean ./Test -C builds); remove .all-tools from the top level repository directory to disable it.

To install the 32-bit libraries on a 64-bit Debian 9 system:

dpkg --add-architecture i386
apt update
apt install libc6-i386

Additional Third-party Tools

The following tools do not currently have any specific support in this repo, but can be useful for testing.

VICE: The Versatile Commodore Emulator

VICE is a suite of simulators for various CBM computers, including PET models, the VIC-20 and the Commodore 64.

MAME Multi-system Emulators

You can install or build the latest version from mamedev.org or just use your system packages; on Debian 9 they'd be installed with:

sudo apt-get install mame mame-tools mame-doc

The documentation installed by mame-doc, under file:///usr/share/doc/mame-doc/singlehtml/index.html, is just an older version of what's found at https://docs.mamedev.org

Additional Tool Information

Playing CMT (Cassette Tape) Images

See r8format:doc/cmtconv.md.

The py65 Monitor

py65 includes a monitor, py65mon, that can be run from the command line. With no options it drops directly into the monitor on a simulated 6502 with 64K RAM.

Options:

• -l FILE: Load file at address $0000.
• -r FILE: Load ROM image at top of address space and reset into it.
• -g ADDR: Goto ADDR after loading files.
• -i ADDR: Location of TTY input register getc (default 0xf004)
• -o ADDR: Location of TTY ouput register putc (default 0xf001)

Addresses given on the command line use C/Python base notation (10, 0xa, 012) rather than the +$ notation used with monitor commands.

Command summary (similar to VICE monitor):

General:

• Readline command line editing available.
• Prefix numbers w/$+% for hex/decimal/binary. radix shows/sets default.
• help [CMD] with for more details.
• quit
• add_label ADDR NAME, show_labels, delete_label NAME: NAME can be used in place of ADDR below, and arithmetic (start+8) may be used.

Display and input:

• ~ NUMBER: Displays NUMBER in all bases.
• registers: display PC AC XR YR SP NV-BDIZC. Set regs with NAME=VALUE, comma-separated.
• mem START:END: Display memory. Show 16-byte lines with width 70.
• fill ADDR[:END] BYTE ...: Deposit byte(s) starting at ADDR. Repeats bytes to END if given.
• disassemble START:END
• assemble ADDR [STMT]: Interactive if no stmt given. Labels may be used.
• load "FNURL" ADDR: Load file or URL (quotes optional) at given address (top for top of memory). (Warning: C64 files will have a two-byte load address at the start of the file that's treated as data.)
• save FNAME START END

Execution:

• reset: Reset CPU and clear memory.
• goto ADDR: Set PC and resume execution
• return: Execute, return to monitor just before next RTS/RTI.
• step: Executes instr, disassembles next instr.
• add_breakpoint ADDR, show_breakpoints, delete_breakpoint ADDR.
• cycles: Display number of cycles since last reset.