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RAM-Box schematic. - Printable Version

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RAM-Box schematic. - Diego Diaz - 12-12-2003


I'm looking for info regarding RAM-box to face my 2004 Non-Volatile RAM module (NoVRAM) personal project. Where "non-volatile" stands for: "Zero power" data retention, no back-up battery or the alike.

Option "A":

Would it be possible to get such a schematic?

Is it available somewhere?

Option "B":

A very, very kind (and confident of me) user that send me a RAM-Box for (non destructive :-) reverse engineering...

Ok, you can stop laughing now...

Have a nice weekend!


Re: RAM-Box schematic. - Emmanuel, France - 12-12-2003

got the following message when sending a mail to you ?!
This Message was undeliverable due to the following reason:

Each of the following recipients was rejected by a remote mail server.
The reasons given by the server are included to help you determine why
each recipient was rejected.

Recipient: <sulacoPSNAMO2000@hotmail.com>
Reason: Requested action not taken: mailbox unavailable

My mail was: - Emmanuel, France - 12-12-2003

Dear Diego,
I can send you mine.
It's a W&W 32K RAMBOX.
2 pages are out of order.
May you can fix and study it?!
You send it back when you have finished.

NoSpam issue. - Diego Diaz - 12-12-2003


Thanks a lot Emmanuel! I've mailed you back with details.

Best regards.

Re: RAM-Box schematic. - Meindert Kuipers - 12-13-2003


I can send you the VHDL of my MLDL2000. But what kind of RAM do you want to use? I have been looking into this myself, and there is something like FRAM, but this is expensive. Today's SRAM's hardly use any power at all and could use a goldcap to keep the contents alive. The other option is FLASH, but erasing is always in banks.


Re: RAM-Box schematic. - Diego Diaz - 12-14-2003

Hi all, Meindert

I've been out for the weekend so excuse me for the late reply.

Your VHDL will be of great interest to me Meindert, thanks a lot for your offer.

Regarding the FRAM/SRAM issue, I haven't still made a decision about it. Anyhow, there are little room inside a module for a gold cap... and they are also quite expensive.
By the other hand, a SRAM chip with a small cap could also keep its contents while unplugged if a "data retention device" is built, and this is easily achieved thru the Clonix programming adapter with a single battery and a 20 pin DIL socket. (just another idea... :-)


Re: RAM-Box schematic. - David Brunell - 12-15-2003

Hi Diego,

Some thoughts on the volatility problem:

1. Why not have both flash and RAM? Have a function to copy the RAM to the flash by command or when the power is turned off.

2. Use a very small lithium cell. Even the commonly-available types are as thin as 1.2 mm.



Re: RAM-Box schematic. - Diego Diaz - 12-15-2003

Hi David,

Thanks a lot for your advices. I've considered the Li Battery option, and it's quite feasible: they're thin and small, and have really long term voltage stability over the nominal volage range for low current drains (wich is the case).

Quite more difficult to handle is the RAM -> Flash approach, the proccess itself is too slow, so chances are that the whole thing goes wrong due to: Module unplug, Calc re-Switching on,... too many different and uncontrolable variables to take care of.

Look forward to *hear* from you soon.



Re: RAM-Box schematic. - Meindert Kuipers - 12-15-2003


I have been thinking about this. If you add RAM to your Clonix and make it MLDL compatible, then you basically have done what I am doing with the MLDL2000. I have no problem with that, I would gladly support you.

My approach with the MLDL2000 is to have SRAM just for Mcode development and storage (HEPAX-like). All fixed things should reside in FLASH. Programming of FLASH is not supported from the HP41 and can only be done under supervision of a PC for technical reasons. It may be very well possible with a microcontroller, but there are some hurdles to be taken.

Biggest problem is to fit everything in a module housing, unless there is a microcontroller available with enough SRAM and FLASH, or if we start using tiny BGA components.

Through my work I do have access to PCB assemblers for this type of technology, but not for free.


Re: RAM-Box schematic. - Diego Diaz - 12-16-2003

Hi all, Meindert,

First of all, thanks a lot for keeping the cooperative spirit alive. As far as I'm concerned this is the main goal in our little HP-41'ers community and we all share its benefits.

Some of us spent, literally, hundreds of hours and $$$ to built a "solution", both for our own joy as well as to serve others needs. I'm pretty sure nobody's going to make a "fortune" on this. And side cash will, in most cases, be re-invested on the next project. May some romantic spirit is on the background after all... :-)

Back on the technical aspects of this thread, I haven't found such a "magic" microcontroller (64kFlash 32kSRAM... 5.5v!! and the required small footprint) So I decided to give a try with "standard" devices, Non-Volatile xx256FRAM + new Flash ROM PIC ┬ÁC.

The required PCB needs, obviously, to be double sided, and the whole layout must be changed too, it must also be manufactured under high quality standards whith very thight tolerances (not a task for one's kitchen or small laboratory, and not cheap either), but it can hopefully fit a standard module housing (I'm quite obsessive about physical space wasting...;-). I'll borrow your contacts for said PCB manufacturing, provided prototyping stage runs OK.

Yes, FRAM is quite expensive, but there's only one chip needed for the job, so I think it would be acceptable. Anyhow, I haven't get the FRAM samples to start prototyping, but I can make a first attempt with standard SRAM as FRAM is pin to pin compatible (timing is not though.)

For now I'm still preparing my Clonix PCB's and populating them with the required components, they'll be for sale at the pace module shells reach my hands. (Not a high rate for now... I must say)

Kind regards.