Early
Electronic
Calculator
Notes

Comments on Calculator Technical Data

Technical data relating to particular calculators has been categorized into 3 levels to indicate the depth of data available: A value with a fractional component indicates the approximate portion of the level available. For example, 2.5 means level 2 (the schematic) is complete and about half of level 3 has been derived.

For levels 2 and 3 the source of data may be either reverse engineering or manufacturer data. With a few exceptions, levels 2 and 3 data presented here (including pinouts for integrated circuits) has been derived from the reverse engineering of various calculators.

For LSI-based calculators a maximum of level 2 will be available without manufacturer technical data.


Comments on Reverse Engineering

With patience, perseverence, and an excessive amount of time on one's hands, reverse engineering can produce an accurate schematic of connections. If the IC-pinouts are available then producing the logic schematic from the connection schematic is trivial. However, if the IC-pinouts are not available, then one must derive the pinouts from the connection schematic. This becomes a specialised puzzle which can be solved with: Viewing the unit in terms of it's functional structure and working from the 'outside' (I/O devices: keyboard, display, clock) to the 'inside' (registers, arithmetic, etc. and finally the state machine) gate inputs and outputs can be identified and with a little conjecture and iteration eventually the picture of the logic emerges.

Having now arrived at the logic schematic and IC pinouts, level 2 of the reverse engineering is complete. This data can now be used to create a simulation of the unit. The simulation permits one to observe the internal functioning in a meaningful and controllable form, and can be used as the basis for deriving level 3 data. The simulation also provides the benefit of proving the accuracy and validity of the level 2 data.

Occasionally, in the process of attempting to identify the internal use of the pin of an IC, there is not enough information or diversity of use to arrive at a firm conclusion. For example, the µPD106 IC in the Commodore DAC-612 is used 2 times but in both cases pins 1,2,8 and 10 are connected to ground. As only one ground connection is necessary it is not possible to discern whether the multiple connections to ground are actually required, are inputs connected to ground as a requirement of the application, or are open pins and just acting as 'ways' for another connection on the printed circuit board. Such pins are marked with a question mark on the IC pinouts.


Key to Headings and Abbreviations

Logic Technology refers to the physical technologies used to implement the logic:

Memory Technology refers to the physical technology used to implement the main register memory:

Display refers to the type of display technology used:

TD Level refers to the depth of technical data available:

A value with a fractional component indicates the approximate portion of the level available. For LSI-based calculators a maximum of level 2 will be available without manufacturer technical data. See also comments on technical data and reverse engineering above.

TD23 Pages is the number of printed pages of level 2 and 3 technical data (primarily the schematic).

TD23 Source is the source of level 2 and 3 technical data:

TD23 Data is the actual level 2 and 3 data:


Downloading and Printing TD23 Data

The GIF files are somewhat pixelated but readable, there is some loss of clarity from the base format which is Clarisworks (Macintosh). Contact via email if interested in obtaining data in another format.

Each page (GIF file) is intended to fit on a standard letter-size page when printed. Retrieving via FTP or saving to a file before printing may be preferable to printing directly from one's browser, as some browsers scale the image and add additional header information when printing.

For multi-page schematics, the set of pages is isolated in a directory and may be downloaded in a single FTP directory-get operation.



  Calculators | Integrated Circuits | Displays | Simulations
EEC
Aug 2000