Summagraphics tablet?

From: Tony Duell <>
Date: Wed May 5 18:34:12 2004

> I have the thing opened up right now. There are 24 DIP switches, three
> banks of eight, labeled SW1 through SW3. The settings currently are


> thus, with bits numbered according to the markings on the switch banks
> and 1=on, 0=off:
> 12345678 <--bit numbers
> SW1 11110110
> SW2 11000010
> SW3 10110110
> There is a good deal of "small" logic, CMOS and TTL in the cases I've
> bothered to look at the numbers on, a bunch of discrete components, and
> three socketed "big chips": a 2732 UVEPROM with a sticker on which is
> handwritten "1103" and "7.9"; a 74C154 (why this is socketed I have no
> idea); and something that looks like a CPU, on which is printed various
> things in various ways; I think it's probably an 8031.

Possibly. The Bit Pad 1 used an 8035. And, IIRC a 2708 EPROM. It was
certainly a 3-rail thing, since one the problems with one of my BP1s was
that the PSU stopped giving the -5V output, the EPROM couldn't be read,
and the microcontroler did nothing useful...

> There's also a momentary pushbutton switch of no obvious function
> (inaccessible with the cover on) labeled SW4 and a six-contact

The BP1 has a reset button, but that's accessible without dismantling the

> card-edge connector of equally obscure function.

No idea. PSU input?

Received on Wed May 05 2004 - 18:34:12 BST

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