DATAMATH CALCULATOR MUSEUM
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DATAMATH CALCULATOR MUSEUM |
Datamath Calculator Museum DCM-50A Playground C-500 Family Adapter
| Date of introduction: | March 29, 2025 | Display technology: | n.a. |
| New price: | Display size: | n.a. | |
| Size: | 3.2" x 4.0" x
0.85" 81 x 102 x 22 mm3 |
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| Weight: | 2.9 ounces, 81 grams | Serial No: | 0001 |
| Batteries: | n.a. | Date of manufacture: | mth 04 year 2025 |
| AC-Adapter: | n.a. | Origin of manufacture: | USA |
| Precision: | Integrated circuits: | ZIF-24 Socket, 2*CD4066, CD40106, SN75369 | |
| Memories: | |||
| Program steps: | Courtesy of: | Joerg Woerner |
When
we were probing early in 2025 for the first time the 24 pins of a General Instrument
GI 250 single-chip calculator circuit soldered on the printed circuit board
(PCB) of a Litton Royal Digit III calculator with its odd 4-digit display, we
realized that the GI 250 Chip is not compatible with our Datamath Calculator Museum
DCM-50A
Platform. Three observations of the GI 250 - better known as Pico Electronics' PICO1 Chip - stood
immediately out:
| • The PICO1 uses a supply voltage of -25 Volts • The Clock Input uses voltage levels of 0 and -25 Volts • The 19 keyboard pins are activated with short pulses between each display scan cycle |
Probing the GI 251 Chip of a Litton Royal V calculator with a more common
8-digit display resulted in another surprise - and obstacle for the DCM-50A Platform:
| • The PICO1 outputs its display information in two groups of 4 digits on the same output pins |
On our quest to document Pico Electronics' PICO1 Chip and its many descendants like the General Instrument C-500, C-550, C-560, C-570 and CZL-550, we developed here at the Datamath Calculator Museum three additional tools for our DCM-50A (PLAYGROUND):
| • DCM-50A (PLAYGROUND)
C-500
Family Adapter: Daughter Board for the DCM-50A (PLAYGROUND)
Frame Carrier for
General Instrument's C-500 Portfolio • DCM-50A (PLAYGROUND) KBD102 Keyboard: Keyboard with 20 individual keys to support the PICO1-style keyboard reading • DCM-50A (PLAYGROUND) Digilent I/O Extender: Plug-In Board to add six additional Input Signals for the Digilent Discovery |
To access all features of the early PICO1 Chips, the schematics and layout of the DCM-50A Playground
G.I. C-500 Family Adapter are providing accordingly:
| • DC/DC Converter for high-voltage PICO1 Chips • Selector Jumper for high-voltage (25 V) or low-voltage (15 V) Chips • 3 LEDs to signal VSS, VDD(LV) and VDD(HV) voltages • Header Pins for all DCM-50A Platform Signals provided by the DCM-50A PG Frame • 100 kHz Clock Oscillator, Selector Jumper for internal/external Oscillator and Level-Shifter • Driver Transistor for Keyboard Enable Signal and Connector to KBD102 Keyboard • Digit Demultiplexer for D15, D26, D37 and D48 Outputs with optional Inverters for Select Signals • Header Pins for various PICO1 Signals • Patch Field for all 24 pins of the PICO1 Chip |
Please notice that the DCM-50A PG DIL42 Adapter needs to be
mounted on top of the DCM-50A PG Frame
Carrier.
If you have additions to the above article please email: joerg@datamath.org.
© Joerg Woerner, June 29, 2025. No reprints without written permission.