Texas Instruments TP0458


Texas Instruments introduced the TMC0980 family of single-chip calculator circuits in June 1976 with the two scientific calculators SR-40/TI-30 and the counterpart Business Analyst for financial applications. Within two years Texas Instruments introduced with the TI-50, TI-53, and Business Analyst II calculators with a similar feature set in a much smaller housing and powered by two small button style alkaline batteries good for more than 1,000 hours of operation time. This tremendous progress was made possible by replacing the power-hungry LED Display with an LC-Display and switching the manufacturing process of the single-chip calculator circuit from a 9V metal gate PMOS process to a 3V metal gate CMOS process. The TP0320 family is based on the TMC0980 design, an extension of the TMS1000 Microcomputer family, but sports a larger data memory. The TP0320 chip includes 18,432 Bits Read-only Memory (ROM, 2k*9 Bits) and 832 Bits Read-access Memory (RAM, 12 Registers * 16 digits, 64 Bits Display), a 4-bit Arithmetic unit, a programmable PLA for segment decoding and both segment and digit multiplexing for a 9-digit LC-Display with up to 66 segments and 3 common scan lines.

Driven to keep the die size of the TP0455 as small as possible while adding new features like timekeeping capabilities and a larger display latch to accommodate LC-Displays with up to 12 digits and both ROM and RAM size the main contributors to the die area, Texas Instruments decided to reduce the RAM size of twelve 16-digit Registers of the TP0320 to only eight Registers and added in lieu of it a 4-bit I/O bus for processor-to-processor communication similar to the failed TP0485 to create Master-Slave architectures using two TP0455 chips and effectively doubling ROM and RAM capacity

The TP0458 introduced in 1986 increased the memory capacity of the TP0456 by 50% to 27,648 Bits Read-only Memory (ROM, 3k*9 Bits) and 768 Bits Read-access Memory (RAM, 12 Registers * 16 digits, allowing for very capable programmable calculators with up to 100 program steps like the TI-62 Galaxy, TI-65 and TI-60 in a Master-Slave architecture. With the TI-30 Galaxy and TI-10 Galaxy/Galaxy Junior only two calculators make use of the TP0458 in a single-chip configuration.

The TP0458 was the last single-chip calculator circuit family manufactured in TI’s metal gate CMOS process, subsequent designs made use of Toshiba’s polysilicon gate CMOS process allowing for operation with solar cells and/or a single 1.5 Volts battery.

Learn more about Texas Instruments’ adventure with their own polysilicon gate CMOS process and the ambitious "LCD III Project" leaving behind the failed   series

The TP0458 chip includes 27,648 Bits Read-only Memory (ROM, 3k*9 Bits) and 832 Bits Read-access Memory (RAM, 12 Registers * 16 digits, 64 Bits Display), a 4-bit Arithmetic unit, a programmable PLA for segment decoding and both segment and digit multiplexing for a 12-digit LC-Display with up to 84 segments and 4 common scan lines. Both chips can work either in a single-chip architecture or in a dual-chip Master-Slave architecture.

The TP0455/TP0456 and its big brother TP0458 with an increased ROM and RAM capacity were very successful and many designs made use of their flexibility with both programmable ROM and segment decoder.

Family Members and Applications

Type Calculator/Product Application Comments
TP0458/CD4805 TI-65 Scientific, 100 steps, Timer Dual chip, Slave - CD4806
TP0458/CD4806 TI-65 Scientific, 100 steps, Timer Dual chip, Master - CD4805
TP0458/CD4808 TI-30 Galaxy, Handy Tech Galixa Speech Scientific Single chip
TP0458/CD4810 TI-62 Galaxy Scientific, 100 steps Dual chip, Master - CD4811
TP0458/CD4811 TI-62 Galaxy Scientific, 100 steps Dual chip, Slave - CD4810
TP0458/CD4812 BA-III Financial Single chip
TP0458/CD4815 TI-60 Scientific, 84 steps Dual chip, Master - CD4614
TP0458/CD4816 Galaxy Junior, TI-10 Galaxy Educational Single chip



  Description Comments
Architecture Single-chip Calculator Scientific, Financial
Category Digit Processor 4-bit digits
Related TP0456 Smaller ROM and RAM
ROM Size 27,648 Bits 3072 Words * 9 Bits
RAM Size 832 Bits 12 Registers * 16 digits
64 Bits Display Register
Outputs 4 Common, 21 Segments Integrated Common Scan Line and Segment Drivers
Inputs 5 Keyboard, CPU-CPU communication Segment to Keyboard Scan-Matrix

Technical Specifications

Item Min Typ Max Unit Comments
VDD   3.0   V   
VSS   0   V   
CK  250 350 450 kHz  Internal oscillator       


The TP0458 is manufactured in a 5 um metal gate CMOS process.

The die size of the TP0458 is approximately 165 mils * 245 mils / 4.2 mm * 6.2 mm.


The TP0458 uses a 0.6” wide 40-pin SPDIP (Shrink Plastic Dual In-line Package with a 0.07” / 1.778 mm lead pitch).

Pin Configuration

TP0458/CD4815 (TI-60 Master)

Pin IO Function Pin IO Function
1   n.c. 40 O LCD COM 1
2 I Key input 1 39 O LCD COM 2
3 O Key row 7, M3DP, M2C, M2F, M2G 38 O Segments
4 O Key row 6, M2D, M2E, M2A, M2B 37 O Segments STAT, DEG, GRAD, RAD
5 I Key input 1 36 O Segments MSIGN, M8E, M8F, M8G
6 O Key row 4, M2DP, M1C, M1F, M1G 35 O Segments M8D, M8C, M8A, M8B
7 O Key row 5, M1D, M1E, M1A, M1G 34 O Segments M8DP, M7E, M7F, M7G
8 I Key input 1 33 I Segments M7D, M7C, M7A, M7B
9 O Key row 1, ESIGN, E2E, E2F, E2G 32 O Segments M7DP, M6E, M6F, M6G
10 O Key row 2, E2D, E2C, E2A, E2B 31 O Segments M6D, M6C, M6A, M6B
11 IO TP0456/CD4555 30 O Segments M6DP, M5C, M5F, M5G
12 IO TP0456/CD4555 29 O Segments M5D, M5E, M5A, M5B
13 I Key input 1 28 O Segments M5DP, M4C, M4F, M4G
14 O Key row 3, PROG, E1E, E1F, E1G 27 O Segments M4D, M4E, M4A, M4B
15 O Key row 8, E1D, E1C, E1A, E1B 26   n.c.
16 I Key input 1 25   n.c.
17 V Negative Voltage VSS 24   n.c.
18 V Positive Voltage VDD 23   n.c.
19 O LCD COM 4 22 O Segments M4DP, M3C, M3F, M3G
20 O LCD COM 3 21 O Segments M3D, M3E, M3A, M3B
The Segment drivers A-G and the Decimal point are connected to a display in the pictured way. 

Keyboard Scan-Matrix

The keyboards of all calculators based on the TP0458 family consist of an x/y-matrix connected to up to eight segment outputs with the top row ([ON] key) connected to VDD and the keymatrix inputs K1, K2, K3, K4, and K5. Keyboards with nine rows have the top row ([ON] key) connected only to VDD

Example for the TI-60 with TP458/CD4815: 

  K1 K2 K3 K4 K5
Row 8 LRN RST SST BST Integral
Row 7 hyp sin cos tan DRG
Row 6 HEX EE log lnX YX
Row 5 SUM+ X<>Y ( ) :
Row 4 STO 7 8 0 *
Row 3 RCL 4 5 6 -
Row 2 EXC 1 2 3 +
Row 1 PI 0 . +/- =


Calculators based on the TP0458 make use of a 12-digit LCD-display with 4 COM (common scan) lines. 

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If you have additions to the above datasheet please email:

© Sean Riddle and Joerg Woerner, January 28, 2021. No reprints without written permission.