Characterization of Single-chip Calculator Circuits - TMS0100 Family

The DCM-50A Platform supports the Characterization of TMS0100 Devices including TMS1802 and TMS1875 in its left-most TMS0100 Textool Test Socket with the voltages V_SS set to 7.2V and V_GG set to -7.2V, accordingly.

TMS1875NC

Device-under-Test:

Keyboard: The Heathkit IC-2008 makes use of a keyboard assembled with individual long-stroke push-button switches arranged in an 11*2 matrix with the rows connected to the D1-D11 Outputs (Display Scan) and the columns connected to the KN (Keyboard Scan Numerical) and KO (Keyboard Scan Operational) Inputs of the TMS1875NC single-chip calculator circuit. The thumb-wheel switch to select the position of the decimal point is connected between the D1-D7 and D10 Output and KP (Keyboard Scan Decimal Point) Input while the latching push-button switch for the Constant Mode is connected between the D10 Output and KQ (Keyboard Scan Constant) Input.

Keyboard Matrix of the Heathkit IC-2008:

Display: The Heathkit IC-2008 makes use of a 9-digit display assembly with three 3-digit Sperry SP-753 planar neon gas discharge "Panaplex II" display modules. The nine discrete high-voltage drivers for the Anodes of the display assembly are connected to the D1-D8 and D11 Outputs (Display Scan) of the TMS1875NC and the 8 discrete high-voltage drivers for the Cathodes to its SA-SG and SP Outputs (Segments) with SH not connected. An additional flip-flop with its clock input connected to the Digit Driver output D11 of the TMS1875NC used for the left-most digit and its two Q and /Q outputs connected to the eight discrete high-voltage drivers. This circuitry changes the pre-programmed scanning order of the TMS1875NC from D11→D10→D9…D1 to D11→D10→D8...D2 / D11→D9→D7…D1 (with D10 and D9 actually not used for the display of an 8-digit calculator), an implementation of the "Interlaced Scan Multiplex Operation" recommended for multiplex operation of SP-700 series displays. The advantage of this approach is that the blanking time normally required within a display envelope to avoid "ghosting" is accomplished while other display envelopes are addressed. The left-most 3-digit Sperry SP-753 display module of the IC-2008 calculator would see a D11→D8 / D11→D7 scanning order, the middle display module a D6→D4 / D5 scanning order, and the right-most display module a D2 / D3→D1 scanning order, fulfilling the 150 us blanking time requirement of the SP-700 Series. The voltage swing for the Anodes and Cathodes of the evaluated Heathkit IC-2008 calculator manufactured in March 1972 was measured with about 80/120 Volts to 220 Volts.

Display Layout:

The Output Decoder PLA of the TMS1875NC is programmed for 7-Segment displays with the following Output Assignments:

Display Fonts:

Scanning: Display and keyboard scanning is performed in D11 → D1 direction at a rate of about 584 Hz with the Digits blanked at State S1 and State S13 but no Segment blanking:

TMS0101NC

Device-under-Test:

Keyboard: The Heathkit IC-2008A makes use of a keyboard assembled with individual long-stroke push-button switches arranged in an 11*2 matrix with the rows connected to the D1-D11 Outputs (Display Scan) and the columns connected to the KN (Keyboard Scan Numerical) and KO (Keyboard Scan Operational) Inputs of the TMS0101NC single-chip calculator circuit. The thumb-wheel switch to select the position of the decimal point is connected between the D1-D7 and D10 Output and KP (Keyboard Scan Decimal Point) Input while the latching push-button switch for the Constant Mode is connected between the D10 Output and KQ (Keyboard Scan Constant) Input.

Keyboard Matrix of the Heathkit IC-2008A:

Display: The Heathkit IC-2008A makes use of a 9-digit display assembly with three 3-digit Sperry SP-753 planar neon gas discharge "Panaplex II" display modules. The nine discrete high-voltage drivers for the Anodes of the display assembly are connected to the D1-D8 and D11 Outputs (Display Scan) of the TMS0101NC and the 8 discrete high-voltage drivers for the Cathodes to its SA-SG and SP Outputs (Segments) with SH not connected. An additional flip-flop with its clock input connected to the Digit Driver output D11 of the TMS0101NC used for the left-most digit and its two Q and /Q outputs connected to the eight discrete high-voltage drivers. This circuitry changes the pre-programmed scanning order of the TMS0101NC from D11→D10→D9…D1 to D11→D10→D8...D2 / D11→D9→D7…D1 (with D10 and D9 actually not used for the display of an 8-digit calculator), an implementation of the "Interlaced Scan Multiplex Operation" recommended for multiplex operation of SP-700 series displays. The advantage of this approach is that the blanking time normally required within a display envelope to avoid "ghosting" is accomplished while other display envelopes are addressed. The left-most 3-digit Sperry SP-753 display module of the IC-2008A calculator would see a D11→D8 / D11→D7 scanning order, the middle display module a D6→D4 / D5 scanning order, and the right-most display module a D2 / D3→D1 scanning order, fulfilling the 150 us blanking time requirement of the SP-700 Series. The voltage swing for the Anodes and Cathodes of the evaluated Heathkit IC-2008A calculator manufactured in May 1972 was measured with about 80/120 Volts to 220 Volts.

Display Layout:

The Output Decoder PLA of the TMS0101NC is programmed for 7-Segment displays with the following Output Assignments:

Display Fonts:

Scanning: Display and keyboard scanning is performed in D11 → D1 direction at a rate of about 584 Hz with the Digits blanked at State S1 and State S13 but no Segment blanking:

TMS0121NC

Device-under-Test:

Keyboard: The Olympia CD101 makes use of a keyboard assembled with individual long-stroke push-button switches arranged in an 11*2 matrix with the rows connected to the D1-D11 Outputs (Display Scan) and the columns connected to the KN (Keyboard Scan Numerical) and KO (Keyboard Scan Operational) Inputs of the TMS0121NC single-chip calculator circuit. The sliding switch to select the position of the decimal point is connected between the D2-D4 and D10 Output and KP (Keyboard Scan Decimal Point) Input. A diode is connected between the D10 Output and KQ (Keyboard Scan Constant) Input.

Keyboard Matrix of the Olympia CD101:

Display: The Olympia CD101 makes use of an 10-digit display assembly with eleven Futaba Vacuum Fluorescent Display (VFD) tubes mounted in a robust frame and soldered directly to the Main printed circuit board (PCB). One Futaba SP8D2 tube is used for the Minus sign and Overflow Indicator while ten 8-segment Futaba DG8R tubes are used for the Numerals. The 11 discrete high-voltage drivers for the Control Grids of the display assembly are connected to the D1-D11 Outputs (Display Scan) of the TMS0121NC and the 9 discrete high-voltage drivers for the Anodes to its SA-SH and SP Outputs (Segments).

Display Layout:

The Output Decoder PLA of the TMS0121NC is programmed for 7-Segment displays with the following Output Assignments:

Display Fonts:

Scanning: Display and keyboard scanning is performed in D11 → D1 direction at a rate of about 584 Hz with the Digits blanked at State S1 and State S13 but no Segment blanking: