Canon Palmtronic MD-8 aka MULTI 8

Date of introduction:  1977 Display technology:  Fluorescent
New price:   Display size:  8 + 8
Size:  6.1" x 3.1" x 0.90"
 156 x 78 x 23 mm3
Weight:  5.6 ounces, 159 grams Serial No:  778058
Batteries:  3*AA Date of manufacture:  mth 12 year 1977
AC-Adapter:   Origin of manufacture:  Japan
Precision:  8  Integrated circuits:  TMC1079 (KBSLΔ7745)
Memories:  1 Displays:  Futaba 20-ST-22
Program steps:   Courtesy of:  Joerg Woerner

Canon introduced already in 1977 with this Palmtronic MD-8 aka MULTI 8 the first pocket calculator using a two-line display. A sliding switch to the left of the Vacuum Fluorescent Display (VFD) selects one of three different operating modes:

MEMORY - The upper display line shows the number in the Memory
SINGLE - The upper display line is not used
PROCESS - The upper display line shows the operand and the lower display line the operator and result

When the calculator is in PROCESS Mode, the lower display shows to the left of the operator the basic function (+, −, ×, ÷), too and allows to check the calculation process.
Dismantling the featured Palmtronic MD-8 manufactured in December 1977 in Japan reveals a very compact design based on a single-sided printed circuit board (PCB) centered around a TMC1079NL single-chip calculator circuit connected to the keyboard and powered by three AA-sized disposable Alkaline batteries.

The TMC1079NL is a member of the TMS1000 Microcomputer family introduced in October 1974 with the SR-16 calculator. While the TMS1000 design was mainly intended for designs using power-hungry LED displays with external display drivers, uses the TMS1070 redesigned output drivers for the 11 R-Outputs (Display Scan) and 8 O-Outputs (Segments) that can withstand voltages up to -35 Volts and hence allows direct operation of low-voltage Vacuum Fluorescent Displays (VFDs).

The Palmtronic MD-8 makes fully use of the TMS1070 design and we could identify on the PCB both the voltage converter to generate a -0 Volts supply for the Futaba 20-ST-22 VFD and the external "pull down" resistors for the R- and O-Outputs. A very similar design was introduced already with the TI-2550 II, the first application of the TMS1070 chip.

If you glance briefly at the two-line display with its total of 18 digits and compare it with the above statement for the TMS1070 supporting only 11 Display Scan Outputs, you might ask yourself: How do the control an 18-digit display with just 11 R-Outputs? And how is the Basic Function Indicator connected to the Microcomputer. Learn more about Characterization of Single-Chip Calculator Circuits with the DCM-50A Platform

The related Canola MD 810 uses similar electronics in a desktop style housing. Within just three years Canon replaced the power-hungry VF-Display with a modern LC-Display and introduced the MD-81.

Don't miss the TI-30X IIS introduced 22 (!) years after the MD-8 and the TI-106 II introduced in 2014.

If you have additions to the above article please email:

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