Texas Instruments TP0455


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 Random-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.

In the midst of the Calculator War end of the Seventies, manufacturing costs of electronic calculators were under extreme pressure and the calculator chip was one of the main cost drivers. The manufacturing costs of an Integrated Circuit (IC) are calculated with:

IC cost = (Die cost + Testing cost + Packaging cost) / Final test yield

With the die cost roughly proportional to the die area, testing and packaging costs roughly proportional to the pin count, and the final test yield mostly inverse proportional to the die area, goals are well defined: Keep the die size as small as possible while adding new features like timekeeping capabilities or a larger display latch to accommodate LC-Displays with up to 12 digits. With 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 16-digit 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 Primary-Secondary architectures using two TP0455 chips and effectively doubling ROM and RAM capacity. The first two products based on the TP0455 made perfectly use of the changes from its predecessor TP0320:

TP0455/CD4501: TI-1745 DataCard Time - adding Time, Alarm Time, Stopwatch and a Timer to the TI-1760 DataCard calculator.
TP0455/CD4505 and CD4506: TI-55-II adding 12-digit LC-Display, statistical functions, conversions and even simple integration
   to the TI-53 while increasing its program memory from 32 to 56 steps.

The TP0455 single-chip calculator circuit sports an undisclosed bug and was soon replaced with the TP0456 and most designs were converted with simply adding 50 to the CD (Custom Design) number following the TP0456, while original TP0456 designs started with CD4601:

TP0455/CD4506A: Original TI-55-II Primary Chip
TP0456/CD4556: Revised TI-55-II Primary Chip
TP0456/CD4614: Original TI-60 Secondary Chip

The TP0455 chip includes 18,432 Bits Read-Only Memory (ROM, 2k*9 Bits) and 576 Bits Random-Access Memory (RAM, 8 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 Primary-Secondary architecture.

The TP0455/TP0456 and its later extension 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
TP0455/CD4501C TI-1745 (DataCard Time) Basic, Time Single chip, not released
TP0455/CD4505A TI-55-II Scientific, 56 steps Dual chip, Slave - CD4506
TP0455/CD4506A TI-55-II Scientific, 56 steps Dual chip, Primary - CD4505
TP0455/CD4507B TI-35, TI-40 Scientific Single chip, replaces TP0324
TP0455/CD4508C TI-2000 (Time Manager) Basic, Time Single chip
TP0455/CD4509B TI-1890 (Converter) Basic, Conversion Single chip
TP0455/CD4511A CA-800 Cassette Interface Single chip
TP0455/CD4512 AC-II not yet discovered Dual chip, Primary - CD4513
TP0455/CD4513 AC-II not yet discovered Dual chip, Secondary - CD4512
TP0455/CD4514B TI-2001 GTI, LOGpit Car, Time Single chip
TP0455/CD4515 TI-30-II, TI-30 LCD Scientific Single chip, replaces TP0320/CD3202
TP0455/CD4518 CMF not yet discovered Single chip
TP0455/CD4519 LCD Programmer Scientific, Base Conversion Single chip



  Description Comments
Architecture Single-chip Calculator Scientific, Financial
Category Digit Processor 4-bit digits
Related TP0320
9-digit, 7-segment LC-Display
Bug fix
ROM Size 18,432 Bits 2048 Words * 9 Bits
RAM Size 576 Bits 8 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 TP0455 was manufactured in a 5 um metal gate CMOS process (metal width = 0.20 mil / 5.0 um, metal spacing = 0.25 mil / 6.0 um, diffusion width = 0.20 mil / 5.0 um, diffusion spacing = 0.20 mil / 5.0 um).

The die size of the TP0455 is approximately 170 mils * 210 mils / 4.3 mm * 5.3 mm.


The TP0455 uses either a 0.4 wide 28-pin SPDIP (Shrink Plastic Dual In-line Package with a 0.07 / 1.778 mm lead pitch)
or a 0.6 wide 40-pin SPDIP (Shrink Plastic Dual In-line Package with a 0.07 / 1.778 mm lead pitch).

Pin Configuration

TP0455/CD4507 (TI-35)

Pin IO Function Pin IO Function
1 IO Key row 5, 3D, 3C, 3A, 3B 28 O LCD COM 1
2 I Key input 2 27 O LCD COM 2
3 IO Key row 3, 3DP, 2E, 2F, 2G 26 I Key input 1
4 IO Key row 4, 2D, 2C, 2A, 2B 25 O Key row 6, 4DP, 3E, 3F, 3G
5 I Key input 3 24 O Segments SIGN, 8E, 8F, 8G
6 IO Key row 1, 2DP, 1E, 1F, 1G 23 O Segments 8D, 8C, 8A, 8BD
7 I Key input 4 22 O Segments 8DP, 7E, 7F, 7G
8 IO Key row 1D, 1C, 1A, 1B 21 O Segments 7D, 7C, 7A, 7B
9 IO Key row 7, STAT, DEG, GRAD, RAD 20 O Segments 6G, 6F, 6E, 7DP
10 I Key input 5 (Wake up) 19 O Segments 6D, 6C, 6A, 6B
11 V Negative Voltage VSS 18 O Segments 6DP, 5E, 5F, 5G
12 VI Key row 8, Positive Voltage VDD 17 O Segments 5D, 5C, 5A, 5B
13 O LCD COM 4 16 O Segments 5DP, 4E, 4F, 4G
14 O LCD COM 3 15 O Segments 4D, 4C; 4A, 4B

TP0455/CD4506 (TI-55-II Primary)

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 2 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 3 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 Pin 7 30 O Segments M6DP, M5C, M5F, M5G
12 IO TP0456/CD4555 Pin 5 29 O Segments M5D, M5E, M5A, M5B
13 I Key input 4 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   TP0456/CD4555 Secondary Pin 16
16 I Key input 5 (Wake up)
TP0456/CD4555 Secondary Pin 10
25   TP0456/CD4555 Secondary Pin 17
17 V Negative Voltage VSS 24   TP0456/CD4555 Secondary Pin 18
18 V Positive Voltage VDD 23   TP0456/CD4555 Secondary Pin 19
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 DP (Decimal Point) are connected to the display in the pictured way. 

Keyboard Scan-Matrix

The keyboards of all calculators based on the TP0455 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-35 with TP455/CD4507:

  K1 K2 K3 K4 K5
VDD x! 1/x % OFF ON/C
Row 7 x2 sin cos tan DRG
Row 6 INV EE log lnx yX
Row 5 SUM+ K ( ) ÷
Row 4 STO 7 8 0 ×
Row 3 RCL 4 5 6
Row 2 SUM 1 2 3 +
Row 1 EXC 0 . +/− =

Example for the TI-55-II with TP455/CD4506:

  K1 K2 K3 K4 K5
VDD 2nd R/S x OFF ON/C
Row 8 LRN RST SST BST Integral
Row 7 hyp sin cos tan DRG
Row 6 INV 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 TP0455 make use of 9-digit or 12-digit LCDs (Liquid-Crystal-Displays) with 4 COM (common scan) lines. 

horizontal rule

If you have additions to the above datasheet please email:

Sean Riddle and Joerg Woerner, January 30, 2021. No reprints without written permission.