DATAMATH CALCULATOR MUSEUM
|
DATAMATH CALCULATOR MUSEUM |
Sharp EL-204
| October 1976 | Display technology: | LED | |
| New price: | Display size: | 8 | |
| Size: | 5.0" x 3.0" x 0.90" 128 x 75 x 23 mm3 |
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| Weight: | 4.1 ounces, 117 grams | Serial No: | 6311589Y |
| Batteries: | 9V | Date of manufacture: | mth 11 year 1976 |
| AC-Adapter: | Origin of manufacture: | Japan | |
| Precision: | 8 | Integrated circuits: | TMS0956 (KGSΔ7642) |
| Memories: | 1 | ||
| Program steps: | Courtesy of: | Ken H. Meine | |
| Download manual: |
(EU: 5.4M Bytes) |
At
first glance looks this early EL-204 calculator like a typical Sharp design of
the Seventies but sports a red LED display instead the more common green Vacuum
Fluorescent Display (VFD) known from many similar products of this timeframe.
Dismantling
the featured EL-204 manufactured in November 1976 in Japan reveals a clean
design based on a single-sided printed circuit board (PCB) for the main
electronics and a double-sided PCB for the keyboard and powered by a disposable
9 Volts battery.
Removing the PCBs from the calculator
housing divulges an unexpected surprise! The EL-204 makes use
of a Texas Instruments TMS0956 single-chip calculator circuit based on the TMS1000
Microcomputer family. The TMS0950
architecture was introduced in 1975 with the
TI-1200 and
TI-1250 and soon replaced with the
TMS0970, one of the most
successful calculator chip designs.
While the TI-1250 uses a 6x4 layout of the keyboard, changed the EL-204 the
layout into a 5x5 matrix adding the sqr(X) function. Reverse-engineering of the
EL-204 calculator demonstrates that the TMS0956 actually is scanning a 7x4
keyboard matrix, a previously unknown feature of the TMS0950 series.
The display module manufactured by Sharp of the EL-204 uses nine small LED chips bonded on
a substrate with an additional magnifying lens to enlarge the digits.
If you have additions to the above article please email: joerg@datamath.org.
© Joerg Woerner, November 25, 2022. No reprints without written permission.