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DATAMATH CALCULATOR MUSEUM |
Canon Palmtronic LD-80
Date of introduction: | 1974 | Display technology: | Fluorescent |
New price: | Display size: | 8 | |
Size: | 5.8" x 3.5" x 1.25" 147 x 89 x 32 mm3 |
||
Weight: | 6.7 ounces, 190 grams | Serial No: | 500476 |
Batteries: | 4*AA Alkaline | Date of manufacture: | mth 12 year 1974 |
AC-Adapter: | AD-1 | Origin of manufacture: | Japan |
Precision: | 8 | Integrated circuits: | TMS0855 |
Logic: | Chain | Displays: | Futaba 9-ST-02A |
Program steps: | Courtesy of: | Joerg Woerner |
Canon
introduced in 1974 with the LD-80 Panther D and its sibling Palmtronic
LD-80
its first Battery-powered Handheld Calculators with Vacuum-Fluorescent Displays
(VFDs),
putting an end to four generations of calculators using Light Emitting Diode (LED)
displays:
• 1st Generation:
LE-10 • 2nd Generation: LE-80, LE-80M, LE-80R, LE-82 • 3rd Generation: LE-81M, LE-100, F-5, FC-80 • 4th Generation: LE-83, LE-84 and LE-85 |
While we suggested previously that Canon introduced first the
Palmtronic LD-80 and followed soon with the identical looking Panther D, do we
question this assumption since we analyzed the electronics of the two
calculators. Looking closely at the printed circuit board (PCB) of the
Panther D calculator shows on both its component and solder side an "X67-6273-02"
reference while the PCB of the LD-80 shows "X67-6279-02". A second number
on the Main-PCB of the Panther D reads "88-3881" while the LD-80 reads
"88-3887", instead. Common sense would based on the sequence of the
numbers suggest that the Panther D
was designed before the Palmtronic LD-80 calculator. The featured LD-80
calculator has a serial number of 500476 and was manufactured (based on
Date codes located on various components on
the PCB) in
December 1974 in Japan. The featured Panther D calculator with its serial number
126907 was manufactured one month earlier in November 1974. We do not know the
numbering scheme used at Canon in the Seventies but it might be an indicator
that Canon started with the Panther D calculator at #100001 and reserved all
numbers up to #499999 for it when it started for the Palmtronic LD-80 with #500001.
All known Panther D calculators sport serial numbers following the #1xxxxx or 2xxxxx
pattern while
all Palmtronic LD-80 show #5xxxxx serial numbers.
Dismantling this Canon Palmtronic
LD-80 calculator manufactured in
December 1974 in Japan reveals a clean
design based on a single-sided printed circuit board (PCB) for the main
electronics, a single-sided PCB for the keyboard and powered by four disposable
1.5 Volts batteries.
The
Main-PCB is centered around a TMS0855 single-chip calculator circuit
manufactured by Texas Instruments and the few remaining components on the PCB
are mainly used to generate the different supply voltages for the TMS0855 and
Vacuum Fluorescent Display (VFD) and to bias the anodes and grids of the display
with respect to its filament.
On our quest
not only to completely understand the differences between
the LD-80 Panther D and Palmtronic LD-80 siblings but also to
Record the ROM
Content of the TMS0855 single-chip calculator circuit, we decided here at the Datamath
Calculator Museum to give both calculators a full "Teardown Treatment" and share
our findings accordingly.
Calculating Unit:
The TMS0855 is closely related to the TMS0800 Product Family and tracing back to
the TMS1802NC, the first available standard calculator building block on a chip,
later renamed into TMS0102. The TMS0800
kept the size of the Instruction ROM (Read-Only Memory), but decreased the Data
Memory from 13 Digits Registers to 11 Digit Registers and added both integrated
Segment Drivers for the LED display and a clock generator. The TMS0850 Product
Family uses redesigned segment and digit output drivers, directly interfacing
with low-voltage VFDs up to 35 Volts and features modified keyboard scanning
inputs that can withstand up to 35 Volts.
With low-cost battery operated
LED calculators in mind, Texas
Instruments added a so-called Timeout
feature to the TMS0800 devices. When no key presses are detected for about 20
seconds, the display blanks out and shows only a '-' in the leftmost digit to
reduce power consumption of the calculator. Looking closely at the PCB traces of
the dismantled Palmtronic LD-80, you'll recognize that Pin 10 (WDK) and Pin 8
(KN) are connected to effectively disable the Timeout feature.
Display: The
Canon Palmtronic LD-80 calculator manufactured
in December 1974 makes use of a 9-Digit low-voltage VFD manufactured by Futaba and
known as Type 9-ST-02A. The display is soldered with its 19 pins directly to the
Main-PCB.
Display Driver: The term "low-voltage" Vacuum Fluorescent Display might
be misleading when used together with a calculator powered by two 1.5 Volt
batteries. Common VFDs used with portable electronic calculators are usually
operated around 30 Volts, significantly higher than the 10 to 15 Volts operating
voltage of single-chip calculator circuits used in the 1970s. While the first
generation of Texas Instruments TMS0100 single-chip calculator circuits lacked
any display drivers and left the choice of display technology to their
customers, focused the second generation products mainly on Light-Emitting Diode
(LED) technology. In or around 1974, most Western calculator designs still
relied on rather expensive LED technology but Japanese companies like Casio,
Sanyo, Sharp and Toshiba started to leverage the lower manufacturing costs of
VFDs, instead. Texas Instruments introduced in 1974 consequently with the
TMS0850 their first product series focused on battery operated VFD calculators
and modified the integrated segment and digit output drivers to withstand up to
-35 Volts. The TMS0850 chips are manufactured in PMOS technology, meaning the
output transistors are "high-side" switching and the most positive voltage of
the chip is labeled VSS for 0 Volt, all other voltages in the
calculator are consequently negative with respect to VSS. Multiplexed
low-voltage VFDs need a voltage difference between its filament and the grids
and anodes of the numbers of around 30 Volts to light up and to avoid "ghosting"
while scanning, the deactivated grids and anodes should be slightly lower than
the filament voltage. Canon went with the LD-80 the traditional way
and uses a power supply with multiple taps for the negative display voltages. The grids and anodes of the VFD are
"pulled-down" with 17 resistors (100k Ohm) to around -30 Volts, the filament is
biased to around -25 Volts and the TMS0855 switches the
relevant grids and anodes to around 0 Volt to lit them up.
Clock: The Canon LD-80 makes use of the internal clock oscillator of the
TMS0850 chip, we identified a resistor with 100 kOhm connected between Pin 14 (REXT/Clock Select) of the TMS0851 and the negative
VDD power supply line, resulting in a clock frequency of about of 189
kHz.
Power Supply: The Canon LD-80 calculator is powered with four
disposable AA-sized 1.5 Volt batteries and uses a complex DC/DC converter module to
generate a total of five voltages:
• VDD - Negative supply for
TMS0855 (-9.1 V) • VGG - Negative supply for TMS0855 (-15.8 V) • VGR - Negative supply for VFD anodes and grids (-29.8 V) • VP - Negative supply for VFD Filament bias (-25.0 V) • VF - AC supply for VFD Filament (2.5 V, 200 kHz) |
We measured the operating current of featured Canon LD-80 calculator:
Mode | Display | Current VBAT = 6.0 V |
Clock Frequency |
Calculating | 0. | 48 mA | 189 kHz |
Calculating | 88888888. | 58 mA | 189 kHz |
Calculating the power consumption at 6 Volts for the Canon LD-80 results in about 290 mW displaying a '0.', about 350 mW with all segments but the minus sign illuminated. Not very impressive, a Canon LE-84 calculator using four disposable 1.5 Volt Alkaline batteries and a simple DC/DC converter for its TMS0801 chip clocks in at around 100 mW displaying a '0.' and 320 mW with all segments lit. And its older sibling LD-80 Panther with its Hitachi HD3633 chip uses with all segments lit slightly less power than this Palmtronic LD-80 displaying '0.'.
Keyboard: The keyboard assembly of the
Canon LD-80 calculator makes use of a keyboard module with a single-sided phenolic-substrate PCB with gold-plated traces for the contacts and spring-loaded conductive rubber elements for its injection molded plastic keys. This technology used by Canon
with many calculators form the early 1970s proved over time as very reliable. The keyboard
PCB is connected with a short 14-pin flat-cable to the Main-PCB.
With
the DCM-50A Platform developed to
Characterize and
Reverse-engineer
Single-chip Calculator Circuits we could proof that the TMS0855 uses the same
Program Code as the TMS0807 known from the
Canon LE-85 and Commodore
885D but disabled the Segment Blanking in State 1 and State 11 of the Digit Times.
Don't miss the Panther 8 and the.Palmtronic 8 mini introduced about 1975.
If you have additions to the above article please email: joerg@datamath.org.
© Joerg Woerner, January 19, 2003. No reprints without written permission.