FarmFax batery for Memory card

[pser1]

Hello,
Does anybody remember what kind of battery should be soldered on the FARMFAX module 16K RAM-ROM?
I remember it was something like 4,8V but I am not sure about that ...
Thanks beforehand!

[robcfg]

Fortunately, we have scanned the Agro Systemes cartridge which is the same as the FarmFax one (it even says FarmFax on the PCB... ).



So, it should be a 3.6v 110mAh battery. Or two, as it seems that there's room for a second battery that would keep power to the second memory bank.

Cheers,
Rob

[Pernod70]

Fortunately, we have scanned the Agro Systemes cartridge which is the same as the FarmFax one (it even says FarmFax on the PCB... ).

Do we know how the RAM is accessed? And is there a ROM dump of this French version?

[pser1]

thanks for this info, Robert
But I am afraid that the FarmFax board (not the french one) was not exactly the same.
I attach here an image showing the battery that is not round as the one shown in your image.
Keeping into account that the SRAM and ROM in that module work at +5V I was hoping that
the battery should be +4,8V but, of course, I may be completely wrong. I am not sure if using just 3V3
would be enough to avoid the SRAM to lose its info.
cheers!

FarmFax - ROM-RAM expansion cartridge.jpg (252.59 KiB) Viewed 636 times

[pser1]

well, after looking at the datasheet for the SRAM chips it seems that any value over 2V would be enough for data retention
So the value 3,6V must be the correct one.
Thanks one more time!

[robcfg]

Ok, here we go!

Do we know how the RAM is accessed? And is there a ROM dump of this French version?

By the looks of the rom, it seems to have a small piece of code to copy the rom contents to the BASIC program area and run it. So I can extract the BASIC program and see how it access the ram.

Back in the day, I seem to have forgotten to upload the dumps and the manual, dear, oh dear...
Please find them in the Upload section: viewtopic.php?f=7&t=11347

thanks for this info, Robert

Always at your service!

But I am afraid that the FarmFax board (not the french one) was not exactly the same.
I attach here an image showing the battery that is not round as the one shown in your image.

Oh, this is very nice!
My board is an Issue 2 board while yours is an Issue 1. I see a lot of common elements but didn't expect them to be also that different.

Could you please take some nice pictures of both sides of your board? I'll take care of adjusting them, correct the perspective and clean them up for the wiki.

Cheers,
Rob

[pser1]

Hi Robert,
I attach here some images related to the FarmFax memory module I have
The zip contains the big files downloaded from my phone.
I hope that is better than reducing them to be shown on screen here
cheers!

FarmFax.zip

(20.14 MiB) Downloaded 34 times

[robcfg]

These pictures are very good, thanks a lot!

[robcfg]

Fortunately, we have scanned the Agro Systemes cartridge which is the same as the FarmFax one (it even says FarmFax on the PCB... ).

Do we know how the RAM is accessed? And is there a ROM dump of this French version?

I've attached the decoded BASIC program, in case anyone would like to take a peek and find how the RAM is accessed.

[robcfg]

I may be wrong, but it looks to me that POKE 65344,1 pages in the cartridge memory and POKE 65344,0 restores the original memory area.