DATAMATH

DATAMATH CALCULATOR MUSEUM

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 V_PP 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.