Date of introduction:  October 1979 Display technology:  LCD
New price:   Display size:  10 + 2
Size:  5.7" x 2.8" x 0.45"
 144 x 71 x 11 mm3
Weight:  3.5 ounces, 98 grams Serial No:  
Batteries:  2*LR44 Date of manufacture:  mth 02 year 1980
AC-Adapter:   Origin of manufacture:  Japan
Precision:  11 Integrated circuits:  CPU: HD43108A
 RAM, DISPLAY: 2*HD43109
Memories:  22    
Program steps:  256 Courtesy of:  Joerg Woerner

Casio Computer Co., Ltd introduced with the FX-501P and FX-502P in October 1979 their first keystroke Programmable Pocket Calculator with LC-Display following the amazing PRO fx-1, trailing Hewlett Packard's legendary HP-41C about three months. The main differences between the FX-501P and FX-502P are the capacity of the user memory:

FX-501P: 128 merged program steps, 11 user memories
FX-502P: 256 merged program steps, 22 user memories

Both FX-501P and FX-502P shared their crowded keyboard and were 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".

The FX-501P series of Programmable Pocket Calculators features a 7-pin connector for peripherals positioned next to the coin batteries on top of the housing:

Product Description MSRP (1979)
FA-1 Cassette Interface  

Dismantling the featured Casio FX-502P manufactured in February 1980 by Casio Computers in Japan reveals a surprisingly clean design centered around a custom-specific 4-bit microcontroller HD43108A and two support chips:

HD43108A: 4-bit microcontroller with integrated RAM and ROM manufactured by Hitachi in a CMOS process and using
   a 56-pin QFP (Quad Flat Pack) package
2*HD43109: Display driver with built in RAM, manufactured by Hitachi in a CMOS process and using
   a 60-pin QFP (Quad Flat Pack) package

horizontal rule

If you have additions to the above article please email:

Joerg Woerner, January 3, 2021. No reprints without written permission.