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Characterization of Single-chip Calculator Circuits - Other Devices

AMI S2144

The DCM-50A Platform supports the Characterization of the S2144 Device with the TMS1000 Textool Test Socket set to DCM-50A (TMS1000) mode and patching (swapping) most of the pins. One additional patch wire is needed to connect the external clock oscillator not available on the TMS1000 Socket but on the TMS0100 Socket or directly through the Digilent Digital Discovery Interface. The voltages VSS and VGG are set to 6.5V and -3.5V, respectively and VDD is patched to the TMS0800 Socket.

Device-under-Test:

Package Markings Top (Upside down): AMI 7333KEO, S2144
Package Markings Bottom: NONE
Donor Calculator: Melcor Model 1000, October 1973

Keyboard: The Melcor Model 1000 makes use of a keyboard with 18 of its 20 switches arranged in an 9*2 matrix with the rows connected to the D1 to D9 Outputs (Display Scan) and the columns connected to the KN and KO Inputs (Keyboard Scan) of the S2144 single-chip calculator circuit. The [ON] and [OFF] keys are used with additional electronics to replace a traditional sliding switch.

Keyboard Matrix of the Melcor Model 1000:

  KN KO
D1 1 ×
D2 2 ÷
D3 3 PD
D4 4 +
D5 5
D6 6 =
D7 7 C/CE
D8 8 0
D9 9 .

Display: The Melcor Model 1000 makes use of an unknown Nine-Digit Calculator Numeric Seven-Segment LED Display module controlled with 2 additional SN75492-style digit drivers from the corresponding Output pins D1 to D9 and the segments SA to SDP driven directly from the S2144 chip.

Display Layout:

Nine-Digit LED Module

The Output Decoder of the S2144 is programmed for 7-Segment displays with the following Output Assignments:

S2144 Pin 23 24 25 26 27 28 2 22
Segment A B C D E F G DP
The Segment drivers A-G and DP (Decimal Point) are connected to the Nine-Digit LED display in the pictured way. 

Display Fonts:

Type Calculator Number Fonts Decimal
Separator
Thousands
Separator
Entry
Overflow
Calculating
Overflow
Minus Memory
Indicator
AMI S2144 Melcor 1000 n.a.     n.a.

Scanning: Display and keyboard scanning is performed in D1 → D9 direction at a rate of about 1,250 Hz with one Blank State after D9:

Instruction Cycle Time (ICT) = 1 Clock = 0.02 ms @ CK=50 kHz
Leading Digit Blanking Time = 0.5 ICT = 0.01 ms
Active Digit Time = 3 ICT = 0.06 ms
Trailing Digit Blanking = 0.5 ICT = 0.01 ms
Blank State D9 → D1 = 4 ICT = 0.08 ms
Display Cycle Time = 40 ICT = 0.8 ms

Mostek MK5020A

The DCM-50A Platform supports the Characterization of Mostek MK5020 Product Family Devices with the TMS1000 Textool Test Socket set to DCM-50A (TMS1000) mode and patching (swapping) most of the pins. One additional patch wire is needed to connect the Segment H output not available on the TMS1000 Socket but on the TMS0100 Socket and an additional "pull-down" resistor is necessary for the Clock Output pin of the MK5020 chip. The voltages VSS and VDD/VGG are set to 9.5V and -5.5V, respectively. Alternatively the MK5020 chip can be placed in the TMS1000 Textool Test Socket set to DCM-50A (TMS0100) mode and Pin 14 isolated.

Device-under-Test:

Package Markings Top: MOSTEK, MK5020A, ASSY IN KOR., 7342 H
Package Markings Bottom: NONE
Donor Calculator: Heathkit IC-2006, November 1973

Keyboard: The Heathkit IC-2006 makes use of a keyboard with 17 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 and KO Inputs (Keyboard Scan) of the MK5020A single-chip calculator circuit. The Constant/Chain sliding switch is connected between D10-KQ.

Keyboard Matrix of the Heathkit IC-2006:

  KN KO KP KQ
D1 1      
D2 2 ×    
D3 3 ÷    
D4 4      
D5 5 +=    
D6 6 −=    
D7 7      
D8 8      
D9 9 .    
D10 0 CE    K
D11   C    

Display: The Heathkit IC-2006 makes use of 3 National Semiconductor NSN33 Three-Digit Calculator Numeric Seven-Segment LED Displays mounted directly on the Main-PCB and controlled with 9 discrete digit drivers and 8 discrete segment drivers from the corresponding Output pins D1 to D9 and SA to SDP of the MK5020A chip with SH not connected.

Display Layout:

3*NSN33

The Output Decoder PLA of the MK5020A is programmed for 7-Segment displays with the following Output Assignments:

MK5020A Pin 16 17 18 19 20 21 22 23 24
Segment A B C D E F G H DP
The Segment drivers A-G and DP (Decimal Point) are connected to the 3*NSN33 display in the pictured way. 

Display Fonts:

Type Calculator Number Fonts Decimal
Separator
Thousands
Separator
Entry
Overflow
Calculating
Overflow
Minus Memory
Indicator
MK5020A Heathkit IC-2006 n.a.     n.a.

Scanning: Display and keyboard scanning is performed in D11 → D1 direction at a rate of about 350 Hz:

Instruction Cycle Time (ICT) = 3 Clocks = 0.02 ms @ CK=150 kHz
Leading Digit Blanking Time = 1 ICT = 0.02 ms
Active Digit Time = 11 ICT = 0.22 ms
Trailing Digit Blanking = 1 ICT = 0.02 ms
Display Cycle Time = 143 ICT = 2.86 ms

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

Joerg Woerner, February 4, 2023. No reprints without written permission.