DATAMATH CALCULATOR MUSEUM

Datamath Calculator Museum DCM-50A (PLAYGROUND)

Date of introduction:	September 21, 2022	Display technology:	LED
New price:	$849.95 (2022 = $119.95 in 1972)	Display size:	12
Size:	10.5" x 8.5" x 1.5" 267 x 216 x 38 mm³
Weight:	17.4 ounces, 494 grams	Serial No:	0001
Batteries:	4*AA	Date of manufacture:	mth 09 year 2024
AC-Adapter:	DC 6V	Origin of manufacture:	USA
Precision:		Integrated circuits:	3SN75493, 2SN75494
Memories:		Displays:	12*HP 5082-7653
Program steps:		Courtesy of:	Joerg Woerner

The Datamath Calculator Museum DCM-50A (PLAYGROUND) is based on the generic DCM-50A Platform to access most features of calculators and certain features of products other than calculators that are not covered by the scope of the DCM-50A (TMS0100, TMS0800, TMS1000, TMS1200 and TMS0900) and the DCM-50A (OTHERS) category.

When we designed here at the Datamath Calculator Museum in 2022 the DCM-50A Platform, we put our main focus on the famous TMS0100 Product Family and its successors TMS0800 and TMS1000. To allow for full compatibility with these chips, the DCM-50A Platform is consequently centered around an 11x4 keyboard matrix, 11 Digit Drivers, 9 Segment Drivers and 28-pin Packages. Later single-chip calculator circuits introduced by Texas Instruments, like the TMS0970, TMS1040 or TMS1270, didn't fit into this architecture and we started to develop various Adapters to be plugged into the TMS1000 Header:

• TMS0900 Adapter: TMS0950, TMS0970, TMC0900
• TMS1040 Adapter: TMS1040
• TMS1270 Adapter: TMS1200, TMS1270, TMS1300, TMS1370

With the additional "Patch Field" for the TMS1000 ZIF-Socket of the DCM-50A Platform, originally intended to accommodate for the different pin-outs of the TMS1000 and TMS1070 chips, we were even able to Characterize some Non-TI Calculator Chips like the AMI S2144 and Mostek MK5020A or the TI TMS3878 Five Decade Counter.

On our mission to Characterize and Reverse-Engineer not only calculator chips manufactured by Texas Instruments, but branching out to offerings from their competitors in the 1970s, namely AMI, Cal-Tex, Commodore/MOS Technology, Electronic Arrays, General Instrument, Hitachi, Litronix, Matsushita, Mitsubishi, Mostek, National Semiconductor, NEC, Omron, RFT, Rockwell, Sharp, Toshiba, and Western Digital, we encountered some challenges:

• It is not economically viable to design for every single-chip calculator circuit its own Adapter
• Only the TMS1000 ZIF-Socket allows for "Pin Patching" but certain signals are not available with the TMS1000
• Not all necessary modifications can be patched and need additional components like diodes, resistors, capacitors and switches
• Some chips are "almost" pin-compatible to the TMS0100 or TMS0800 ZIF-Sockets but need modifications to unlock their full potential
• Some chips use larger 36-pin, 40-pin or even 42-pin housings instead the 28-pin ZIF Sockets provide with the DCM-50A Platform
• Most chips are not compatible with the different Clock Oscillators available on the DCM-50A Platform

With the DCM-50A (PLAYGROUND) we created a modular approach to tackle these challenges and designed three different printed circuit boards (PCBs) that can be stacked on top of the DCM-50A Platform:

• DCM-50A (PLAYGROUND) FRAME: Plug-In Carrier to access all voltages and signals from the DCM-50A Platform
• DCM-50A (PLAYGROUND) DIL42: Daughter Board with 42-pin ZIF Socket, Patch Field, Diode Matrices, Push Buttons, SPDT Switches and Pin-Modifiers
• DCM-50A (PLAYGROUND) BB400: Daughter Board with Solderless Breadboard (400 connections), Push Buttons and SPDT Switches

To further increase the flexibility of the DCM-50A Platform, an additional keyboard can be mounted on top of the original keyboard:

• DCM-50A (PLAYGROUND) KBD123: 12x3 Switch Matrix Keyboard with Patch Field for Selector Switches with Diode Matrix

With this flexible tool on hand, we are planning to focus on different single-chip calculators circuits introduced in the 1970s and competing with the offerings from Texas Instruments:

• Hitachi Calculator Chips
• Mostek Calculator Chips
• NEC Calculator Chips
• Sharp Calculator Chips

With many of the single-chip calculator circuits either designed for proprietary applications or developed for OEM manufacturers, available documentation of their features is rather scarce and we are committed to provide as much information as possible to the calculator enthusiasts and we document our observations and findings here.

The Technology Section of the Datamath Calculator Museum features under Calculator Chips "Datasheets" of the various products.

Characterization of Single-chip Calculator Circuits

• HITACHI Calculator Chips

The DCM-50A (PLAYGROUND) supports the Characterization of many Non-TI single-chip calculator circuits with up to 42-pin packages using the DCM-50A Playground DIL42 Adapter mounted on top of the DCM-50A PG Frame Carrier. Alternatively, the more flexible - but less comfortable - DCM-50A Playground BB400 Adapter can be used.

Device-under-Test:

• HD3633 - Lloyd's Accumatic 30 (February 1975)
• HD36290 - Lloyd's Accumatic 30 (May 1975)

• NEC Calculator Chips

Device-under-Test:

• µPD940 - Lloyd's Accumatic 30 (September 1975)
• µPD941 - MBO de Luxe I (December 1975)

• Sharp Calculator Chips

Device-under-Test:

• LI2002 - Lloyd's Accumatic 30 (August 1974)
• LI2003

Reverse-engineering of Single-chip Calculator Circuits

Work-In-Progress.

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