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Toshiba BC-8111B

Date of introduction:  1979 Display technology:  Fluorescent
New price:  DM 25.00 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:  C 17661
Batteries:  2*AA Date of manufacture:  mth 01 year 1979
AC-Adapter:  BH-115 (110V) or
 BH-116 (220V)
Origin of manufacture:  Taiwan
Precision:  8 Integrated circuits:  TMS1045 (MT 8001)
Memories:  1 Displays:  Futaba 9-ST-08A
Program steps:   Courtesy of:  Joerg Woerner

This Toshiba BC-8111B "Basic with Memory" calculator followed the otherwise identical BC-8111 and shares its internal design with the BC-8018B "Basic" and BC-8112SL "Enhanced Basic" 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-8111B calculator manufactured in January 1980 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.

Looking closer onto the PCB you'll notice two diodes labeled D4 and D5 and placed somehow between the TMS1045 and the keyboard assembly - at first glance an unusual approach. Preparing our DCM-50A Platform to allow the Characterization of Single-Chip Calculator Circuits of the TMS1040 Family, we reverse-engineered the BC-8111B calculator and understood that Texas Instruments started to add with the TMS1040 a "virtual" 5th Keyboard Input line by using two additional diodes emulating the 5 K Inputs of the TMC0980 Family. While the TMS0100 single-chip calculator circuit introduced the concept of an 11x4 keyboard matrix scanned with the 11 Digit Outputs and 4 Keyboard Inputs, would the reduction to just 9 Digit Outputs of the TMS1040 allow for only 9x4 keys and switches, in some calculator applications like the Canon F-31 a show-stopper. Adding an extra "virtual" Keyboard Input allows consequently for a 9x5 keyboard matrix and this BC-8111B arranges its 24 keys within a 9x4 grid.



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

Joerg Woerner, July 3, 2002. No reprints without written permission.