DATAMATH

DATAMATH CALCULATOR MUSEUM

Datamath Calculator Museum DCM-50A Playground LED Direct-Drive Frame Carrier

Date of introduction:	February 6, 2025	Display technology:	n.a.
New price:		Display size:	n.a.
Size:	3.2" x 4.0" x 0.45" 81 x 48 x 11 mm³
Weight:	1.2 ounces, 34 grams	Serial No:	0001
Batteries:	n.a.	Date of manufacture:	mth 02 year 2025
AC-Adapter:	n.a.	Origin of manufacture:	USA
Precision:		Integrated circuits:	CD4077
Memories:
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. It consists of 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 of the DCM-50A Platform
• DCM-50A (PLAYGROUND) LED DD FRAME: Plug-In Carrier to access all voltages and signals of the DCM-50A Platform for Chips with LED Direct-Drive capability
• 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

The DCM-50A Platform was developed for single-chip calculator circuits with external display drivers and consequently are digit drivers used for the Digit Outputs D1 to D11 and segment drivers used for the Segment Outputs SA to SH and SP. Most calculator chips were manufactured in the early 1970s in PMOS (p-Channel MOS) technology, meaning the output transistors are "high-side" switching and for the so-called multiplexed common cathode LED displays in use with all LED-based calculators, the digit drivers are "inverting" the polarity of the Digit Outputs. Calculator chips with LED Direct-Drive capability have these "inverters" already integrated, rendering them incompatible with the DCM-50A Platform. To overcome this limitation, incorporates the LED Direct-Drive Frame Carrier for each Digit Output a small transistor to revert the polarity of the signals back. This modification of the output signal polarity creates an issue with chip designs using the Digit Outputs for keyboard scanning, consequently are optional inverters for the keyboard scanning inputs available, too.

To access all features of single-chip calculator circuits with LED Direct-Drive outputs, the schematics and layout of the DCM-50A Playground LED DD FRAME Carrier are providing accordingly:

• V_SS, V_DD and V_GG access from TMS0100 and TMS0800 Pin-Headers
• Digit Outputs D1 (rightmost) to Digit Outputs D11 (leftmost) access from TMS0100 Pin-Headers with level-translators from
the LED Direct-Drive low-side switching digit drivers to DMC-50A compatible high-side switching digit drivers
• Jumper-Header (black) to enable optional Digit Outputs D0
• Selectable pull-down voltage V_DD and V_GG for Digit Outputs D0 to D11 with Switch (red)
• Segment Outputs SA to SH and SP from TMS0100 and TMS0800 Pin-Headers
• Keyboard Inputs KN, KO, KP and KQ TMS0100 and TMS0800 Pin-Headers with Switch (white) to select Non-Inverting or Inverting polarity
• TMS0100 CLK Oscillator from Jumper-Header J9
• Digital Discovery DIN0, DIN21 and DIN22 Signals from Jumper-Headers J10, J11 and J12, respectively
• Digital Discovery DIO24 and DIO25 Signals from Jumper-Headers J9 and J13, respectively

Please notice that the DCM-50A Playground LED Direct-Drive Frame Adapter needs to be plugged into the leftmost TMS0100 and center TMS0800 Pin-Headers on the DCM-50A Platform. It also connects to five Jumper-Headers on the DCM-50A Platform.

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