apple1cartridge

This repository contains firmware files for the "Apple-1 RAM/ROM Cartridge" expansion card for the Apple-1 computer.

Description

This project aims to provide Apple-1 users with a quick way to expand RAM capacity in their systems up to 52 KB and to simultaneously store some Apple-1 programs in ~30KB of on-board ROM, which can be banked in and out via software. The on-board ROM also contains a loader program which is capable of loading programs spanning across noncontinuous memory locations.

The A1C expansion card allows via the physical switch to completely disable the ROM/loader program functionality which takes up to the 2 KB of memory ($4000-$47FF) and to provide continuous 44KB wide RAM address space instead.

Memory map

Physical switch in ROM mode:

address	function
$1000-$3FFF	RAM region #1
$4000	the start address of the on-board loader program
$47F8-$47FF	write to these memory locations causes ROM to be banked in or out depending on the least significant bit of the address, A0=0 - ROM banked out, A0=1 - ROM banked in
$4800-$BFFF	RAM region #2 when ROM banked out
$4800-$BFFF	ROM with program contents when ROM banked in

Physical Switch in RAM mode:

address	function
$1000-$BFFF	RAM region

Contents

The contents of this repository are as following:

• inc/ - contains Apple-1 programs in binary format, the package is downloadable here
• mapping/ - contains EQN and JED files for GAL22V10 based address decoder
• scripts/ - a bunch of useful python scripts which allow conversion from binary to Woz monitor format and vice versa
• src/ - contains the 6502 assembly sources for the Apple-1 RAM/ROM Cartridge onboard ROM loader program

Requirements

You need the following to successfully build the firmware:

• xa cross assembler
• Some software capable of translating the EQN files into JED's. I used for this purpose the DOS based EQN2JED from OPALjr PLD Development Package. This is only required if you wish to make some changes to the GAL based address decoder. The default JED file should be fine for most users.

How to build?

To build the firmware just type:

make

And to clean the build:

make clean

How to customise?

In order to customise your ROM contents you have to edit the src/rom_content.a65 source file. You can find the entry table structure documentation in the source file.

PCB

The KiCad project files with board design and schematics can be found here:

http://github.com/flowenol/Apple1CartridgePcb

Applesoft BASIC support

The onboard ROM loader program can also automatically load your Applesoft BASIC programs thanks to the branch of the applesoft-lite project which has been modified to make use of the A1SI expansion card:

http://github.com/flowenol/applesoft-lite

How to install hardware?

Just put the board in right orientation (as marked on the PCB) in the Apple-1 expansion slot. Or you can use the port expander if the on board slot is already occupied:

https://github.com/flowenol/Apple1ExpanderPcb