23XX Replacement ROM
The 23XX is a replacement ROM for the 2316 / 2332 / 2364 ROMs which is used on many old retro computers like the Commodore and Atari.
The original 23XX rom is a 24 pin chip which is no longer manufactured. In order to replace this you needed to use a 28 pin to 24 adapter so that you could use a 27CXXX ROM. As the 27CXXX chips are also no longer manufactured this leads to stock problems. The 28 to 24 adapter is also larger than the original 23XX which can lead to physical space issues, and the 27CXXX also requires a UV light to erase.
This is where this design comes in. It uses a modern and available SMD flash EPROM while keeping the 24 pin package, so it’s no larger than it needs to be, and can be easily re-programmed with the required optional extra hardware.
This design also makes correct use of the CS2/CS3 active high/low lines, which in many adapters are hardwired to VCC/GND.
Commodore for some reason decided to have multiple versions of the 2332 and 2364 with different active high/low CS pins. This design caters for all these options by setting various solder jumpers.
Purchasing Options:
- 23XX EPROM- The EPROM only which can be set for 2316 / 2332 / 2364 depending on the jumper configuration (See below) Included in the price I can write a ROM of your choice and set the required jumpers. Contact me you send me the ROM and how you would like it configured with active high/low CS lines/.
- 23XX Programmer Adapter – The adapter allows you to connect the 23XX ROM above to a suitable programmer like the TL866 in order to re-program it. You will need to purchase the programming adapter only if you plan to re-reprogram the chip (The TL866 is not included in the sale)
- 23XX EPROM Including Programming Adapter.
Jumper Configuration:
- 2316 (/CS1 /CS2 CS3) 18: Short 2-3 20: Short 2-3 21: Short 2-3 4: Shorted
- 2332 (/CE1 CE2) A: Shorted 18: Short 1-2 20: Short 2-3 21: Short 2-3 4: Shorted
- 2332 (/CE1 /CE2) A: Shorted 18: Short 1-2 20: Short 2-3 21: Short 2-3 0: Shorted
- 2364 (/CE1) A,C: Shorted 18: Short 1-2 20: Short 2-3 21: Short 1-2 0: Shorted
- 2364 (CE1) A,C: Shorted 18: Short 1-2 20: Short 2-3 21: Short 1-2 2: Shorted
The instruction manual for re-programming the 23XX using the adapter can be downloaded here. (It requires a few solder jumpers to be set before programming)
If you are not concerned about the physical space of the 23XX to 27XXX adapter and can source 27XXX ROM’s I also sell the 23XX adapters here
All configuration options have been tested on real hardware, as well as my custom Retro ROM Tester available here
