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UEF2ROM - a UEF to ROM Conversion Tool for Acorn Electron ROM Cartridges

This repository contains a tool for modern computers that converts UEF files containing representations of cassette software for the Acorn Electron to ROM images for use in ROM cartridges or sideways ROM expansions.

The tool requires Ophis to be installed in order to assemble 6502 code needed for the ROM images it creates:

https://michaelcmartin.github.io/Ophis/

Features

I've implemented three things in my ROMs that make it possible to convert cassette-based games to one or two ROM images:

  1. A persistent ROM pointer that can be used to remember where in the ROM the filing system was reading from, so that when it gets the inevitable initialisation call, it doesn't automatically return to the start of the data.
  2. Code to intercept *TAPE calls - surprisingly few games need this.
  3. A ROM bank variable that is set by the first and second ROMs so that when the first ROM is encountered after the second ROM has been read (thanks to an init call) it can pretend it can't handle the call, leaving the filing system to go looking for files in the second ROM.

The last of these is useful because I split files across ROMs and this confuses the filing system, causing it to finish reading the split file in the second ROM, but then returning to the first ROM to look for any following files. If I don't either reset the persistent pointer or reject the call, an invalid pointer is used and I get a "Bad ROM" error.

See http://stardot.org.uk/forums/viewtopic.php?f=2&t=1095 for a discussion about similar tools.

Usage

The UEF2ROM.py script is (over)complicated and provides many options to help produce heavily customised ROMs based on existing, unmodified UEF files. However, it might be possible to convert a small UEF into a single ROM using the following command:

UEF2ROM.py -a -m -s <UEF file> rom1

If the contents of the UEF file does not fit into the number of ROMs, it is possible to either use two ROM images or compress files using the -c option and a colon separated list of load addresses. For example, to compress the files to fit into one ROM:

UEF2ROM.py -a -c e00:x -m -s <UEF file> rom1

Alternatively, to use two ROMs:

UEF2ROM.py -a -m -s <UEF file> rom1 rom2

If a pair of ROMs is not enough then compression can be specified for the files that fit into one of the ROMs:

UEF2ROM.py -a -c e00:x/ -m -s <UEF file> rom1 rom2

Using x in a list of load addresses indicates that the corresponding file in the UEF file should not be compressed. If you omit a load address for a file then the meta-data in the UEF file will be used. The / character separates the load addresses used for the files in each ROM.

If the software in the UEF file performs *TAPE commands, making it fail when run from ROM, code to suppress this system call can be inserted into the generated ROM with the -t option. This is typically used with the -w option to specify where the suppression code should be stored in RAM, as in the following example:

UEF2ROM.py -a -m -t -w 39f <UEF file> rom1

Because different pieces of software use different parts of memory, some experimentation may be needed to find a suitable memory location for the tape suppression code.

Limitations

There are many other options to use to work around issues with many existing UEF files. However, not all UEF files can be used as they are. Many contain too many files to fit into two ROMs, though the tool does support a paging mechanism for the Mega Games Cartridge that allows long sequences of ROMs to be created. Others rely on filing system features that are not supported by the ROM filing system that this tool relies on. Additionally, a lot of software written in the 1980s was designed to only run from tape-based systems and contains hostile checks for expansion hardware. Some of these can be bypassed but this tool does not provide a general solution for this problem.

Licenses

Both the assembly language routines and the Python modules and tools are licensed under the GNU General Public License version 3 or later:

Copyright (C) 2016 David Boddie <david@boddie.org.uk>

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.

According to the GPL FAQ, an installer and the files it installs are considered to be separate works:

http://www.gnu.org/licenses/gpl-faq.html#GPLCompatInstaller

This means that compliance with the above license with respect to the routines provided in this package is independent of compliance with the license of the code or data you include in an assembled ROM file.

The code or data you include in an assembled ROM file will retain its original copyright and license which must be handled accordingly. Including a work in an assembled ROM file does not exempt you from any obligations you have under that work's license.