Sharp PC-1211 strange



#25

I have several Sharp PC-1211 but one of them has a circuit that others do not.
Can anyone tell me what is?


#26

Interesting. Mine doesn't have it either. Looks like a hack job. Is it a connector ? Can't tell from the photo.

#27

What does the other side of the brown board look like? Are there any actual components on it?


#28


#29

Apparently it's a Dual D-Type Flip-Flop. That's all I know though...

So it can't be doing more than remembering two single boolean states of whatever the wires connected to it represent.

#30

Is there a switch on it? (magnetic reed switch perhaps?) to select an extra RAM bank?

Edit: On seeing your second photo (the IC is a flip-flop), perhaps a bank change is done using a POKE command? (E.g. similar to using a 32Kb module in the PC-1500).

Edited: 21 Aug 2011, 11:48 a.m.


#31

The PC-1211 BASIC command set does not include PEEK and POKE.


#32

Perhaps the state is change-able through some I/O commands or something?

#33

is it possibly an early production version where they needed to add a flip-flop to fix a bug?


#34

the serial number is compared to other very recent.
#35

Looks like this is not the only one:

J'ai un circuit en trop sur mon 1211 !!

No plausible explanations though.

#36

The date of the flip-flop is 1992, as these were originally produced in the early '80s this mod was done long after.

This certainly also does not look like a one-off type add-on PCB, it seems like the mod was intended to be for a number of units. I would guess an upgrade similar to the HP-200LX memory upgrades. Hence my suspicion that it might have to do with a memory upgrade, however it may have to do with some other custom added functionality. One would have to trace out the wires/tracks to see exactly where it all connects to.


#37

Wire assignments clockwise from farther left yellow one, if I haven't done any mistake:

    yellow: D
yellow: Q
red/white: VDD
blue/white: VSS
red/white: CK

Not of much help though.


#38

One would also need a circuit diagram for the 1211, or reverse engineer it, a lot of trouble for something not more than a novelty :(


#39

The second D-type flip-flop is not used, as we can gess by the shorted pins. This document mentions a controller inferface for a submersible pump. Two excerpts therein:

"The heart of the timer control package is a Sharp PC1211 pocket
computer with16K memory capability. This has been slightly modified by
hard wiring an external plug to the key pad and battery contacts of the
PC1211."

"At the end of the "delay" time, the PC1211 sends a "Beep 2"
signal which reverses the state of 1/2CD 4013 flip-flop."

Might that PC-1211 be a remnant of that system?


Edited: 21 Aug 2011, 7:34 p.m.


#40

This image from the Vintage Calculators Web Museum shows the exact same modification--right down to the color of the wires involved.

My vote is that this is a factory modification necessary for certain hardware revisions.

Mark Hardman


#41

Quote:
My vote is that this is a factory modification necessary for certain hardware revisions.

Very likely, as there appears to be a lot of them.

Gerson.


#42

Wow. Well if that's a factory mod, it's a pretty sloppy one. The little board is just loose in there and could potentially short. They should have at least used some rtv or other material to secure and insulate it.


#43

No, not a factory mod, but a third party mod. As I mentioned previously, the date of the flip-flop IC is about 10 years after the initial production of the units (and like the 200LX mods I mentioned which were also 3rd party mods). The fact that a custom etched PCB was used shows that it certainly was not a "one-off", so I would expect some number of these modified units to exist.

#44

This certainly seems a most likely explanation - exactly the kind of thing I would expect.

#45

Now, could you verify, for the sake of curiosity, a funny "feature", if it works?

I have a Sharp PC-1430 and I discovered a buffer overflow error that would allow you to replace the password without damaging the stored program much.

The trick is to fill the input buffer completely (I think it's 80 character long) and, when full, pressing the insert key repeteadly. You will see that you are actually dumping memory contents. At least on a PC-1430 you even see characters not available to BASIC programs. (Not available on the keyboard and if I recall correctly the BASIC doesn't have a CHAR() function).

One of the most frequent "alien" characters you see is "~", which I guess is 0.

So, if you keep pressing INS and dumping memory, which not only dumps it, but seems that shifts some contents, you will eventually fill the password with "~~~~~~~~".
Now you just clean up the input buffer so that you keep eight tildes, insert PASS " before and hit enter. And voila!


#46

The PC-1210/11/12 used two four-bit microprocessors sharing the work, probably because they couldn't put enough ROM in a single CMOS microprocessor at that time. The microprocessors used "Harvard architecture", which means that the RAM and ROM weren't even in the same address space, and that the ROM contents can't be read as data in the same way as the RAM. The user memory was in an external chip, so there were actually five independent memory address spaces in the part (compared to two in the HP-41C and only one in more typical computers). This makes it unlikely that there is any clever way in the PC-1211 to get at memory that you're not supposed to from the keyboard, and I've never heard of anyone finding a way to do it.

Sharp used a single eight-bit processor (usually LH5801/3, SC61680, or related parts) in almost all later models. (The PC-1600 has the 61680 and a Z-80.) These processors use a conventional "von Neuman architecture", with the ROM and RAM in a unified address space. That gives a lot more potential for making them do interesting, unintended ("NOMAS") sorts of things.

If anyone has a broken PC-1210/11/12, it would be interesting to decap and photomicrograph the two microprocessor chips, as the folks at Visual6502 have done with other microprocessors.


#47

Quote:
The user memory was in an external chip, so there were actually five independent memory address spaces in the part (compared to two in the HP-41C and only one in more typical computers). This makes it unlikely that there is any clever way in the PC-1211 to get at memory that you're not supposed to from the keyboard, and I've never heard of anyone finding a way to do it.

Anyway, in the PC1430 I'm sure I read RAM, not ROM. The curious characters were simply the result of reading arbitrary numbers.

My 1430 has an upgraded RAM. It's possible to solder a second 6116 chip.


#48

On the later ones, it is possible to get at RAM or ROM by various means, because they are in a single, shared address space. My point was that it would be almost impossible to do anything like that on the 1211 family.


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