Sharp EL-5100

Date of introduction:  June 1979 Display technology:  LCD dot matrix 
New price:  $100.00 (MSRP 1979) Display size:  24 characters
Size:  2.8" x 6.9" x 0.40"
 70 x 175 x 10 mm3
Weight:  4.0 ounces, 114 grams Serial No:  91032669
Batteries:  3*LR44 Date of manufacture:  mth 10 year 1979
AC-Adapter:  n.a. Origin of manufacture:  Japan
Precision:  12 Integrated circuits:  CPU: SC43153
 DISPLAY, RAM: 3*SC43125
Memories:  11    
Program steps:  80 Bytes Courtesy of:  Ken H. Meine

Sharp Corporation introduced in June 1980 with the PC-1211 (and its sibling PC-1210) the World's first Pocket Computer with BASIC programmability. While it looks at first glance like a continuation of this EL-5100, a keystroke Programmable Pocket Calculator introduced in June 1979, did the PC-1211 add another medal to the impressive list Sharp's Calculator Innovations:

Micro Compet QT-8D (Oct. 1969): World’s first electronic calculator incorporating LSI ICs
EL-8 (Nov. 1970): World’s first battery operated portable calculator
EL-805 (May 1973): World’s first COS electronic calculator
EL-8020 (1976): World’s first calculator using Film Carrier System and yellow LCD
EL-8026 (1976): First electronic calculator with solar cells (disputed)
EL-8130 (1977): World’s first touch key calculator
EL-8152 (1979): World’s first 1.6mm-thin electronic calculator
PC-1211 (1980): World's first Pocket Computer with BASIC programmability

We assume that both Hewlett Packard and Texas Instruments, leading in 1980 the market or Programmable Pocket Calculators were impressed by the Sharp PC-1211 and its identical twin Tandy Pocket Computer PC-1, the former company introduced roughly one year earlier with their HP-41C the successor of the ancient HP-67 and the latter was working on "Project X" with the goal to replace its legendary TI-59 and regain leadership in the cat and mouse game with Hewlett Packard.

Learn more about the demanding "Project X" initiated already in Summer 1977 and leading not only to the (failed) TI Programmable 88, but the TI-66 PROGRAMMABLE, failed TI-76 PROGRAMMABLE, Compact Computer CC 40, (failed Compact Computer CC 70) and last but not least the successful TI-74 BASICALC and TI-95 PROCALC.

This Sharp EL-5100 keystroke Programmable Pocket Calculator, introduced in Summer 1979 together with its siblings EL-5101 and EL5102 with smaller displays and the EL-5103 sporting a traditional "portrait" style appearance, introduced a new concept of programming. With the EL-5100 advertised as "Scientific Calculator speaking a new language", a subtle [AER] (Algebraic Expression Reserve) position of a small switch allows the user to enter a Formula with up to 80 characters as it would be written in a textbook:

[AER] A2 + B2
COMP: Answer 13

Dismantling this Sharp EL-5100 manufactured in October 1979 by Sharp Corporation in Japan reveals a clean design based on just one printed circuit board (PCB) populated with a 4-bit microcontroller and three Integrated Circuits (ICs) to drive the alphanumeric LC-Display with 144*7 pixels and provide additional memory space for the calculator.

The PCB of the featured EL-5100 is very similar to the larger of the two PCBs found with the PC-1210 and PC-1211 and sports the listed Integrated Circuits:

SC43153: CPU - 4-bit microprocessor manufactured by Sharp in a CMOS process and using a 62-pin QFP (Quad Flat Pack) package
3*SC43125: Display driver with built in RAM (128*4 Bits), manufactured by Sharp in a CMOS process and using a 62-pin QFP (Quad Flat Pack) package

The 4-bit microcontroller share a common data bus with the three Display chips. One display chip holds the 11 memory registers, one provides the space for the Formula Program, and one provides scratchpad space for the microcontroller.

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© Joerg Woerner, January 24, 2021. No reprints without written permission.