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Toshiba BC-8112SL

Date of introduction:  1979 Display technology:  Fluorescent
New price:  DM 29.00 Display size:  8
Size:  5.6" x 3.0" x 0.8"
 142 x 75 x 20 mm3
   
Weight:  3.9 ounces, 110 grams Serial No:  G 15240
Batteries:  2*AA Date of manufacture:  year 1979
AC-Adapter:  BH-115 (110V) or
 BH-116 (220V)
Origin of manufacture:  Taiwan
Precision:  8 Integrated circuits:  TMS1045 (MT7919)
Memories:  1 Displays:  Futaba 9-ST-08A
Program steps:   Courtesy of:  Joerg Woerner

This Toshiba BC-8112SL "Enhanced Basic" calculator followed the otherwise identical BC-8112SR and shares its internal design with the BC-8018B "Basic" and BC-8111B "Basic with Memory" calculators. The rather unusual approach to use identical electronics for three calculators with a quite different feature set was made possible with Texas Instruments' introduction of the cost-effective TMS1040 Product Family based on the TMS1070 "computer-on-a-chip" introduced in 1974 with the original TMS1000. But we have to credit Canon releasing the full potential of the TMS1040 with its "Almost Scientific" F-31 calculator in 1977.

Comparing the functionality of the three Toshiba calculators and the Canon F-31 demonstrates the bandwidth of products made possible with the TMS1045 single-chip calculator circuit:

Calculator M+ +/- 1/x x2 x % PI () 2-0-F
Toshiba BC-8018B           * * *     
Toshiba BC-8111B *        * * *    
Toshiba BC-8112SL *   * * * * * *  
Canon F-31 * * * * * * * * *

Dismantling the featured BC-8112SL calculator manufactured in 1979 by Zeny Corporation in Taiwan reveals a very cost effective design using a single-sided printed circuit board (PCB) centered around a TMS1045 single-chip calculator circuit connected to a 9-digit Vacuum Fluorescent Display (VFD), a keyboard assembly and powered by 2 AA-sized alkaline batteries.

While the earlier TMS1070 can directly interface with low-voltage VFD up to 35 Volts does it still need external resistors and a zener diode to bias the anodes and grids of the display with respect to the filament. The TMS1040 added an extra VPP pin to connect a negative 30 Volts bias voltage for its modified output drivers. With the TMS1070 featuring 11 R Outputs for the Digits, 8 O Outputs for the Segments and 4 K Inputs for the Keyboard, reduced the TMS1040 the number of R Outputs to 9, consequently are all known TMS1040 calculator designs using a 9-digit VF Display.



If you have additions to the above article please email: joerg@datamath.org.

Joerg Woerner, October 26, 2002. No reprints without written permission.