Characterization of Single-chip Calculator Circuits - TMS1000 Family

The DCM-50A Platform supports the Characterization of 28-pin TMS1000 Devices in its right-most TMS1000 Textool Test Socket with the voltages VSS set to 9.5V and VDD/VGG set to -5.5V, accordingly for devices of the 15V Series. The later 9V Series requires different voltage settings with VSS set to 5.5V and VDD/VGG set to -3.5V.



Package Markings Top: REGENCY 501-374, BSP 7731
Package Markings Bottom: ⚫DP1116BS, SINGAPORE
Donor Product: Radio Scanner Regency ACT-T16K, October 1977

Keyboard: The Regency ACT-T16K makes use of a keyboard with touch-sensitive switches arranged in a 9*4 matrix with the rows connected to the R0-R8 Outputs (Display Scan) and the columns connected to the K1-K8 Inputs (Keyboard Scan) of the TMS1116NL single-chip calculator circuit. The Squelch sliding switch is connected between the R9 Output and K2 Input.

Keyboard Matrix of the Regency ACT-T16K:

  K1 K2 K4 K8
R0 (D1) SS 1 0 [--]
R1 (D2) SC 3 2  
R2 (D3) MA 5 4 CL
R3 (D4) SP 7 6 .
R4 (D5) PR 9 8  
R5 (D6) C4 C3 C2 C1
R6 (D7) C8 C7 C6 C5
R7 (D8) C12 C11 C10 C9
R8 (D9) C16 C15 C14 C13
R9 (D10) [--] [SQUL]    

Display: The Regency ACT-T16K makes use makes use of National Semiconductor NSA578 Seven-Digit Calculator Numeric Seven-Segment LED Display module controlled with 2 additional SN75492-style digit drivers from the corresponding Output pins R0 to R6 and the segments SA to SDP driven directly from the TMS1116 chip. The 16 discrete Channel LEDs are connected through Digit Drivers to R7 and R8, leaving the Search LED on R9, segment DP.

Display Layout:

National Semiconductor NSA578

The Output Decoder PLA of the TMS1116NL is programmed for 7-Segment displays with the following Output Assignments:

TMS1116 Pin 17 16 15 14 13 12 11 10
TMS1116 Port O0 O1 O2 O3 O4 O5 O6 O7
Segment DP A B C D E F G
The Segment drivers A-G and DP (Decimal Point) are connected to the National Semiconductor NSA578 display in the pictured way. 

Display Fonts:

Type Product Number Fonts Decimal

Scanning: Display and keyboard scanning is performed in R0 → R9 direction at a rate of about 150 Hz followed by an RX State to display the Decimal Point. R9 State is stretched to read in signals not generated by the keyboard through a Quad 2-Line to 1-Line Data Selector connected to the four K1-K8 Inputs (Keyboard Scan) of the TMS1116NL:

Instruction Cycle Time (ICT) = 6 Clocks = 0.02 ms @ CK=300 kHz
Leading Digit Blanking Time = 4 ICT = 0.08 ms
Active Digit Time R0 → R8 = 20 ICT = 0.40 ms
Active Digit Time R9 = 64 ICT = 1.28 ms
Active Digit Time RX = 20 ICT = 0.40 ms
Trailing Digit Blanking = 1 ICT = 0.02 ms
Blank State R9 → R0 = 22 ICT = 0.49 ms
Display Cycle Time = 341 ICT = 6.82 ms

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