[Coco] EEPROM selection

[RETRO Innovations]

On 7/26/2024 7:50 PM, Neil Cherry via Coco wrote:
> On 7/26/24 19:14, coco--- via Coco wrote:
>> All
>>
>> Is there an EEPROM that can work at either 3.3 or 5 V and can
>> replace the Coco 3 motherboard ROM.
>> I saw an article about how to use the GPIO of a raspberry pi at
>> https://www.instructables.com/Raspberry-Pi-Python-EEPROM-Programmer/
>> I wondered if such a setup could read a coco ROM and write to a
>> EEPROM chip suitable for a replacing the coco ROM and also
>> which chip would you recommend for this purpose the chip used in
>> the example is 4X the memory of a coco3 ROM.
>>
>> Charlie
>>
>
> I don't know of any EEPROMs (or flash or other types of ROMS) that
> are 3v3 and 5v0 tolerant.
>
Neil's right, no EEPROM or FLASH option is available.  You could make a
battery backed SRAM option, as there are quite a few SRAMs that will run
on both voltages, and there is this:

https://www.digikey.com/en/products/detail/infineon-technologies/FM18W08-SG/4090358

FRAM.  It will hold the value, but is RAM, so easy to program. Just
switch off the !WE line to make it ROM.  No battery needed, but you'd
need to buy something like this (or make something like this):
https://www.ebay.com/itm/225251010393 to adapt the SOIC footprint to DIP.

Jim