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My plan:

Using a PC-interface, one might be able to load programs into the 33s, and read them back into the PC. One might also be able to program "unprogrammable" keystrokes like the "GTO .nnn".
If the goal is oonly to load and store programs, and not entering calculations from the PC, it shouldn't be too hard to modify the 33s.

Necessary modifications:
We want to read and change the contents of the ram, so there is a need to propagate the pins of the ram-chip to the outside of the case. Depending on the type (serial/parallel), it means soldering 5 to 27 wires to the ram-chip.

The 33s could then be plugged into the interface ( consisting of a microcontroller or some logic-chips ) that is connected to the PC.

What I have to do:

1. buy a 33s

2. open it and identify the ram-chip

3. solder the wires

4. build the interface

5. analyse the way programs and variables are stored

6. write a compiler/decompiler

Since one is not able to read the ROM, this should be perfectly legal.

Any help is appreciated! I would like to hear some comments about my plan, too! Klaus

2. open it and identify the ram-chip

It's a commodity 32K SRAM, nothing special

it means soldering 5 to 27 wires to the ram-chip [...]
3. solder the wires

That's going to be the tricky part. It's a bare die under a blob of epoxy. If you're lucky, you might be able to get at the traces that connect it to the Sunplus processor, but it's quite likely that some of those traces will be on the wrong side of the PCB.

Since one is not able to read the ROM, this should be perfectly legal.

If it was able to read the ROM, it would still be perfectly legal. At least in the US; maybe there are some strange laws in other countries, though usually the US is just about the worst as far as ridiculous "intellectual property" laws (e.g., DMCA).

5. analyse the way programs and variables are stored

The variables might simply be stored in the on-board RAM of the Sunplus processor. Programs and equations must be in the separate RAM chip, though.


I am interested to know more! Being able to backup programs would be very convenient.

Especially the prospect of being able to create new recongnizable commands like GTOXYYYY !


Come on guys... Just buy a calc that has the capabilities you want.... These discussions can verge on the absurd....

Sorry if my comments offend you, I am sure some see your efforts as noble...

Only the Hp41c series has what these fellows want: A pocket calculator with I/O.

The 42s holds the most promise in that perhaps a boot up program could be keyed in and then the serial I/O capabilities could be tapped into. There is no POCKET calculator today that does what they want. Sure, there are plenty of graphics and for many people this is fine (must be most people, else we should have a pocket solution by now). I suspect PDA's will invade this sector and satisfy (perhaps wrong word, but fill this niche) 90% of this market, leaving to few customers for a real pocket calculator to be worth marketing.

I am planning on returning to my Hp42s after using my Hp33s as soon as I can. It isn't that the Hp33s is bad, it is actually quite good (for what it is). And it does address the shortcomings of the Hp32s (insufficient memory). But it doesn't compare in real number crunching ability to a 42s. But for 90+% of the RPN calculator crowd, it is sufficient. For the rest of us, well, we aren't worth the extra $0.50 in material (I/O port, and long variable names and other software issues) to pursue. As far as Hp (or Ti, or Casio, or Sharp) is concerned, the high end pocket calculator geek can be satisfied with a new PDA. We will adapt, is their belief (I don't believe this to be true, as a calculator is the perfect tool for napkin or other on the fly engineering). Many engineers have abandoned this philosphy and the Business model certainly discourages this.