• VECTREX DEVELOPER
  

• 64K FRAM PCB Board for the Vectrex cartridge slot

• Freely use up 57.75K of persistent RAM for programming and for applications
  
• Easily develop and run custom BIOS versions on the Vectrex
• Easily flash binary images to any memory address, either with an EPROM burner, or directly from a PC over USB cable connection
  
• Easily use external cartridges with flashed custom BIOS
  

Project Status

• Some time ago I started experimenting with using a Hitachi 6309 CPU in the Vectrex and with programming custom BIOS versions (see here). I used nes4life's Multi BIOS PCB, which worked great, but removing the PCB from the inside of the Vectrex console and plugging it in again each time I needed to flash a new version, turned out to be very cumbersome for BIOS development.

• At some point in 2023, I talked about this to Andreas Reber, who is a colleague of mine and an expert for embedded systems and hardware design, with a long experience in that field, reaching back to the days of the ATARI ST, for which he built several hardware extensions.
  

• Together we came up with ideas and a concept for an extension cartridge for the Vectrex which allows for a smooth and easy development of Vectrex system-software and applications. This translates to that I told him a long list of wishes, and he designed and built a great and powerful toy for me to play around with: the Vectrex Developer.
  

• The Vectrex Developer PCB can be inserted directly into the Vectrex cartridge slot.

• On the board, there are two ZIF-sockets, each of which can hold a removable 32K FRAM. An FRAM works like a Flash-RAM and retains its contents after power-off.

• The left socket is mapped to the lower 32K of the Vectrex address space (0x000-0x7fff), the right socket is mapped to the upper 32K (0x8000-0xffff). For more on the memory mapping see the respective section below.

• The board also holds an FTDI UART interface chip, and a USB cable connector for communication with a laptop or PC.

• On the very right side of the board, there is also an additional external Vectrex cartridge slot.

• For the Vectrex Developer cartridge to work, the internal Vectrex BIOS chip needs to be removed (unsoldered) from the console's digital board.

• This sounds worse than it actually is. Just remove the back cover of the Vectrex, and the chip can easily be unsoldered by working from the bottom-side of the digital board. There is no further disassembly of the console necessary.
  

• It is a good idea to solder in a chip-socket while being at it. Then the original BIOS chip can easily be reinserted again at any time, and the console is restored to its original state.

• When the internal BIOS chip is not present, then the Vectrex CPU will now read the respective BIOS addresses (0xe000-0xffff) from the Vectrex cartridge slot, and thus from the Vectrex Developer cartridge.

• In fact, the Vectrex CPU will now read (and write) any address from the cartridge slot, except for the 0xd000-0xdfff range, which is still internally mapped to the VIA, and for the 0xc800-0xcfff range, which is still mapped to the internal 1K Vectrex RAM.

• Any other address is routed to the cartridge slot, meaning that the full range from 0x0000-0xc7fff and from 0xe000-0xffff is now FRAM, which amounts to a total of 58K, and which can now freely be used by the programmer (well almost, the range from 0xc700-0xc7ff is mapped to the FTDI UART and reserved for the USB communication, see section below).

• Plug the Vectrex Developer into the cartridge slot of the console.
  

• Flash any BIOS and Mine Storm version you like to 0xe000-0xffff range of the upper FRAM of the Vectrex Developer.

• Flash any binary you like to the FRAM range of 0x0000-0xc6ff (~49.75K) and run it with the chosen BIOS.

• Or leave the lower ZIF-socket empty and attach any cartridge to the external cartridge connector and then run the cartridge with the chosen BIOS.

• There is no need to remove the Vectrex Developer from the console's cartridgeslot. Flashing the FRAMs can be done by removing the chips from the ZIF-sockets and by using an EPROM burner, or by leaving them inside the ZIF-sockets and by writing data to them which is obtained from a laptop or PC over the UART USB connection.
  

• For the current version of the Vectrex Developer, I have written a boot loader which is started when the console boots or resets. In our setting, the upper FRAM contains the boot loader and three different BIOS versions (6809, 6309 emulation mode, 6309 native mode).
  

• The boot loader itself is a regular Vectrex program which is executed by the Vectrex CPU. It detects whether there is a 6809 or a 6309 CPU present in the console, and then copies the respective BIOS version to the BIOS memory space and boots the BIOS. The boot loader also allows to switch between emulation mode and native mode in case of a 6309 CPU.

• In addition to that, the boot loader furthermore offers the possibility to read files from the USB UART and to write the obtained data to any desired memory location.
  

• On the PC side, the Vectrex Developer is automatically registered as a serial COM-port device, and a simple terminal program is sufficient to communicate with the Vectrex and to upload files.

• At the moment, I am using the HTerm program. Copying files to the FRAMs this way is actually a lot faster than with an EPROM burner.

• With the Vectrex Developer, binaries and games that use the BIOS routines can effortlessly have sizes up to ~48K. If the BIOS routines are not needed, then the available size increases to ~56K. Any portion of this can be used for RAM variables as well as for code.

• Having all RAM instead of ROM also allows for implementing fancy things like self-modifying code.

• In combination with using the Hitachi 6309 CPU, the Vectrex turns into a very powerful upgraded system with ~56K RAM, and the extended instruction set and increased performance of the 6309, which opens up some very interesting programming possibilities and a new universe to explore.

• The UART offers an easy means of bidirectional communication with the outside world that can be used in any Vectrex program. For example, expensive computations could be outsourced and handled by an external program running on a laptop or PC which communicates its results back to the Vectrex program. I am thinking about trying this for fun with Kingslayer Chess, with the Vectrex sending the chess board configuration to some PC chess program which then computes the moves and sends them back.

• More experiments and reports will follow.
  

• The hardware needed for assembling the current version of the board costs approximately 90 Euros.

• UART interface IC: FTDI FT245RNL
• FRAM IC: FM1808B-SG
  

• The current version of the Vectrex Developer board is actually our second physical prototype. Andreas and I had lots of discussions, and our concept went through many iterations. There was a first alpha prototype which had no external cartridge connector. Also, the lower FRAM was fixedly attached and soldered to the board, and a ZIF-socket was used only for the upper FRAM, see pictures below.
  

• Support: Timo Schwaab, Head of the Electronics Workshop at Pforzheim University

• Hardware: Andreas Reber
• Software: Peer Johannsen

• Feedback is very welcome.
• Email: vectrex@pforzheim-university.de