DATAMATH CALCULATOR MUSEUM
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DATAMATH CALCULATOR MUSEUM |
Characterization of Single-chip Calculator Circuits - TMS0800 Product Family
The DCM-50A Platform supports the Characterization of TMS0800 Devices in its middle TMS0800 Textool Test Socket with the voltages VSS set to 10.0V and VGG set to -5.8V, accordingly.
Device-under-Test:
| • Package Markings Top: TMS0851NL,
P7515 • Package Markings Bottom: J0851P • Donor Calculator: Sovrin Model 128, May 1975 |
Keyboard: The Sovrin Model 128 makes use of a keyboard assembly with 19 snap action switches and a sliding power switch mounted on a double-sided printed circuit board (PCB). The switches are arranged in a 9*3 matrix with the rows connected to the D1-D9 Outputs (Display Scan) and the columns connected to the KN, KO and KP Inputs of the TMS0851NL single-chip calculator circuit. The Timeout feature of the TMS0851NL is enabled with a the [D] key connected to DK Output and KN Input of the TMS0851N.
Keyboard Matrix of the Sovrin Model 128:
TMS0851 | |||
| KN | KO | KP | |
| D1 | 9 | 0 | |
| D2 | 8 | . | |
| D3 | 7 | % | |
| D4 | 6 | ÷ | |
| D5 | 5 | x | |
| D6 | 4 | − | |
| D7 | 3 | + | |
| D8 | 2 | = | C |
| D9 | 1 | ||
| DK | D | ||
Display: The
Sovrin Model 128 makes use of a 9-digit Futaba 9-ST-12 low-voltage
Vacuum Fluorescent Display (VFD) connected directly to the respective 9 Digit
Outputs (Display Scan) and 8 Segment Outputs of the TMS0851NL and biased
to approximately -32 Volts with external pull-down
resistors.
Display Layout:
| Futaba 9-ST-12 |
 |
The Output Decoder PLA of the TMS0851NL is programmed for 7-Segment displays with the following Output Assignments:
| TMS0851 Pin | 26 | 27 | 28 | 1 | 2 | 3 | 4 | 5 | 25 |
| TMS0851 Port | SA | SB | SC | SD | SE | SF | SG | LV | SP |
| Segment | A | B | C | D | E | F | G | DP |
| The Segment drivers A-G and DP (Decimal Point) are connected to the Futaba 9-ST-12 display in the pictured way. Segment H is not connected and the Pin used as LV Input, instead. |  |
Display Fonts:
| Type | Calculator | Number Fonts | Decimal Separator |
Entry Overflow |
Calculating Overflow |
Minus | Seg. H Low V. |
| TMS0851NL | Sovrin Model 128 |
 |
 |
 |
  |
 |
 |
Timeout: The
TMS0851NL implements a so-called Timeout feature. 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. Timeout is
recoverable with an optional [D] key connected between the WDK Output and either
the KN or KO Inputs, or pressing any key assigned to the keyboard scan matrix
D8, D9/KN, KO, KP. We captured with a Digilent Digital Discovery Logic Analyzer
connected to a TMS0851NL and operated in the DCM-50A Platform, the transition
between normal operation and Timeout, before returning with pressing the [D] key
back to normal operation. The TMS0851NL actually "remembered" the previous
content of the display.
Scanning: Display and keyboard scanning is performed in D9 → D1 direction at a rate of about
370 Hz with the Digits blanked at State S1 and State S9:
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• State Time = 4 Clocks = 0.025 ms @ CK=160 kHz • Digit Time = 11 States (1 Instruction Cycle) = 0.275 ms @ CK=160 kHz • Scan Time = 10 Digit Times (D1 to D10 with D10 a dead cycle) = 2.75 ms @ CK=160 kHz |
Device-under-Test:
| • Package Markings Top: TMS0852NC,
7445-1 • Package Markings Bottom: B0852 • Donor Calculator: TI-150, November 1974 |
Keyboard: The TI-150 makes use of a keyboard assembly with 19 Klixon™ hermetic snap action switches mounted on a printed circuit board (PCB). The switches are arranged in a 9*3 matrix with the rows connected to the D1-D9 Outputs (Display Scan) and the columns connected to the KN, KO and KP Inputs of the TMS0852NC single-chip calculator circuit. The Timeout feature is not implemented in the TMS0852NC but still "disabled" with a hard-wired connection between DK and KN on the Main-PCB.
Keyboard Matrix of the TI-150:
TMS0852 | |||
| KN | KO | KP | |
| D1 | 9 | 0 | |
| D2 | 8 | . | |
| D3 | 7 | ||
| D4 | 6 | ÷ | |
| D5 | 5 | x | |
| D6 | 4 | − | |
| D7 | 3 | + | |
| D8 | 2 | = | CE |
| D9 | 1 | C | |
| DK | |||
Display: The
TI-150 makes use of a 9-Digit Panaplex Style
7-Segment display assembly manufactured by Texas Instruments. Here at the
Datamath Calculator Museum we refer to this display as "DIS-PS9" till we learn
about its actual part number.
Display Layout:
| Texas Instruments DIS-PS9 |
 |
The Output Decoder PLA of the TMC0852NC is programmed for 7-Segment displays with the following Output Assignments:
| TMC0852 Pin | 26 | 27 | 28 | 1 | 2 | 3 | 4 | 5 | 25 |
| TMC0852 Port | SA | SB | SC | SD | SE | SF | SG | LV | SP |
| Segment | A | B | C | D | E | F | G | DP |
| The Segment drivers A-G and DP (Decimal Point) are connected to the DIS-PS9 display in the pictured way. Segment H is not connected and the Pin used as LV Input, instead. | |
Display Fonts:
| Type | Calculator | Number Fonts | Decimal Separator |
Entry Overflow |
Calculating Overflow |
Minus | Seg. H Low V. |
| TMC0852NC | TI-150 | |
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Timeout: The so-called Timeout feature used with the TMS0800 Product Family is not implemented in the TMS0852NC programming.
Scanning: Display and keyboard scanning is performed in D9 → D1 direction at a rate of about
370 Hz with the Digits and Segments blanked at State S1 and State S9:
|
• State Time = 4 Clocks = 0.025 ms @ CK=160 kHz • Digit Time = 11 States (1 Instruction Cycle) = 0.275 ms @ CK=160 kHz • Scan Time = 10 Digit Times (D1 to D10 with D10 a dead cycle) = 2.75 ms @ CK=160 kHz |
Device-under-Test:
| • Package Markings Top: TMS0855NCΔ,
A7435 • Package Markings Bottom: J0855A 35 • Donor Calculator: Canon LD-80, December 1974 |
Keyboard: The Canon LD-80 makes use of a keyboard assembly with 19 conductive rubber switches switches arranged in a 9*3 matrix with the rows connected to the D1-D9 Outputs (Display Scan) and the columns connected to the KN, KO and KP Inputs of the TMS0855NC single-chip calculator circuit. The Timeout feature of the TMS0855NC is disabled with a hard-wired connection between DK and KN on the Main-PCB.
Keyboard Matrix of the Canon LD-80:
TMS0855 | |||
| KN | KO | KP | |
| D1 | 9 | 0 | |
| D2 | 8 | . | |
| D3 | 7 | ÷ | |
| D4 | 6 | × | |
| D5 | 5 | − | |
| D6 | 4 | + | |
| D7 | 3 | = | %± |
| D8 | 2 | CI | |
| D9 | 1 | C | |
| DK | -TR- | ||
Display:
The Canon LD-80 makes use of a 9-digit Futaba 9-ST-02A low-voltage Vacuum
Fluorescent Display (VFD) connected directly to the respective 9 Digit Outputs
(Display Scan) and 8 Segment Outputs of the TMS0855NC and biased to
approximately -30 Volts with external pull-down resistors.
Display Layout:
| Futaba 9-ST-02A |
 |
The Output Decoder PLA of the TMS0855NC is programmed for 7-Segment displays with the following Output Assignments:
| TMS0855 Pin | 26 | 27 | 28 | 1 | 2 | 3 | 4 | 5 | 25 |
| TMS0855 Port | SA | SB | SC | SD | SE | SF | SG | LV | SP |
| Segment | A | B | C | D | E | F | G | DP |
| The Segment drivers A-G and DP (Decimal Point) are connected to the Futaba 9-ST-02A display in the pictured way. Segment H is not connected and the Pin used as LV Input, instead. | |
Display Fonts:
| Type | Calculator | Number Fonts | Decimal Separator |
Entry Overflow |
Calculating Overflow |
Minus | Seg. H Low V. |
| TMS0855NC | Canon LD-80 |
 |
|
|
  |
|
 |
Timeout:
The
TMS0855NC implements a so-called Timeout feature. 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. Timeout is
recoverable with an optional [D] key connected between the WDK Output and either
the KN or KO Inputs, or pressing any key assigned to the keyboard scan matrix
D8, D9/KN, KO, KP. We captured with a Digilent Digital Discovery Logic Analyzer
connected to a TMS0855NC and operated in the DCM-50A Platform, the transition
between normal operation and Timeout, before returning with pressing the [C] key
back to normal operation. The TMS0855NC actually "remembered" the previous
content of the display before clearing it due to the [C] key, the optional [D]
key would have preserved the previous calculation.
Scanning: Display and keyboard scanning is performed in D9 → D1 direction at a rate of about
370 Hz with the Digits blanked at State S1 and State S9:
|
• State Time = 4 Clocks = 0.025 ms @ CK=160 kHz • Digit Time = 11 States (1 Instruction Cycle) = 0.275 ms @ CK=160 kHz • Scan Time = 10 Digit Times (D1 to D10 with D10 a dead cycle) = 2.75 ms @ CK=160 kHz |
If you have additions to the above article please email: joerg@datamath.org.
© Joerg Woerner, September 18, 2024. No reprints without written permission.