This repository contains two projects to create a Amstrad Plus / Amstrad GX4000 cartridge, which I started in 2010. Anyway, I had no time to finish or produce them, so maybe there is somebody else interested in them and wants to take over :-)!?
In the "simple-cartridge" folder, you will find the schematics and board layout for a simple flash cartridge for the Amstrad Plus / Amstrad GX4000 cartridge. You can equip it either with an CPLD (XC9536) with ACID protection emulation (see http://www.octoate.de/wp/articles/acid-verilog-code/ for more information) or a real ACID protection chip. It uses an AT29F040 to store the ROM data.
Also designed in 2010, the folder "flash-cartridge" contains an idea for a USB programmable flash cartridge. The idea was to connect the cartridge to a PC and program it and - after that -, you can connect it to the Amstrad Plus or the Amstrad GX4000 and run your program / game. I decided to use an Atmel ATMega8 for the USB connection and to program the flash EPROM (e.g. an AT29C040). Because the ATMega8 does not support USB out of the box, I intended to use the software V-USB stack for Atmel microcontrollers by Obdev (http://www.obdev.at/products/vusb/index.html). To save pins on the microcontroller, I decided to use some shift-registers, which can be accessed by the hardware SPI of the ATMega microcontroller. In the schematics you can find the CARTGND signal, which is connected to GND1 in the schematic and to PD7 of the ATMega microcontroller. The idea about this is to detect if the cartridge is connected to the Amstrad Plus / Amstrad GX4000. The internal pull-up of PD7 normally will return "high" if you read PD7, but if it is connected to the CPC, you will get a "low" value on this pin, which you can use to disconnect the microcontroller from the bus. A Xilinx XC9536 VQFP is used for ACID protection emulation. A bootloader pin was introduced to give you the ability to flash a new firmware to the ATMega8 via the USB bus. Maybe a subproject of the V-USB can be used for that.
The folder "library" just contains a library for Cadsofts / Farnells EAGLE EDA program, which contains the layout of a Amstrad Plus / Amstrad GX4000 cartridge.
The "emulation" folder contains the Verilog description for the ACID protection, which you can use to program a CPLD or an FPGA with the dedicated design tools. For more information about the emulation you can visit http://www.octoate.de/wp/articles/acid-verilog-code
(c)2010-2014 Tim Riemann aka Octoate