Date of introduction:  November 1981 Display technology:  
New price:  $49.00 (MSRP 1981) Display size:  
Size:  4.0" x 8.9" x 0.95"
 102 x 225 x 24 mm3
Weight:  7.6 ounces, 215 grams Serial No:  1B111A
Batteries:  3*AA Alkaline Date of manufacture:  mth 11 year 1981
AC-Adapter:   Origin of manufacture:  Japan
Precision:   Integrated circuits:  CPU: HD43110
Program steps:   Courtesy of:  Joerg Woerner

Sharp Corporation introduced in June 1980 with the PC-1210 (and its sibling PC-1211) the World's first Pocket Computer with BASIC programmability. It took only about three months and Matsushita defined with their Panasonic HHC a new category of Hand-held Computers or Portable Computers. Main competitor in Japan, Casio Computer Co., Ltd, on the other hand introduced with the FX-501P and FX-502P in October 1979 their first keystroke Programmable Pocket Calculator with LC-Display, succeeded in March 1981 with the FX-601P and FX-602P, introducing a dot matrix LC-Display and laying the foundation for the FX-702P "Pocket Computer". Casio took a different approach than Sharp and added BASIC programmability to a Scientific Calculator and labeled the device with "Programmable Calculator" accordingly. Casio's early advertisement featuring the FX-702P used often a big headline "More Power To Your Pocket" to challenge rival Sharp.

The FX-702P Programmable Calculators features not only an internal expansion slot for a memory cartridge but a 7-pin connector for peripherals on its left side:

Product Description MSRP (1981)
FA-2 Cassette Interface
(Fits FX-501P/FX-502P/FX-601P/FX-602P, too)
FP-10 Mini Printer, electro-sensitive FP-36 paper, up to 20 characters per line, 2 lines per second
(Fits FX-601P/FX-602P, too)
(not released) 4k Bytes RAM module with backup battery  
(not released) 8k Bytes RAM module with backup battery  

Dismantling the featured Casio FA-2 Cassette Interface manufactured in November 1981 by Casio Computers in Japan reveals an unexpected complex design centered around a 4-bit microcontroller and powered by three AA-sizes Alkaline batteries.

The HD43110 microcontroller is translating the bit-stream from the FX-702P Pocket Computer into two different tones with a frequency of around 1,2 kHz and 2.4 kHz, following the so-called Kansas City Standard:

HD43110: 4-bit microcontroller with integrated RAM and ROM manufactured
   by Hitachi in a CMOS process and using a 28-pin DIP (Dual In-line Package) encapsulation

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Joerg Woerner, January 5, 2021. No reprints without written permission.