Texas Instruments IC - Integrated Circuits

Texas Instruments invented the integrated circuit (IC) in the year 1958. The first calculators with integrated circuits used DTL (Diode Transistor Logic), RTL (Resistor Transistor Logic) or TTL (Transistor Transistor Logic) elements. These IC's are small building blocks with typical 4 logic gates or 2 flip-flops in a 14 to 16 pin plastic housing. To get a working calculator you need more than 50 of them. The Cal-Tech project demonstrated in 1967 a calculator using only 3 LSI circuits (Large Scale Integration) with more than 1000 transistors per circuit. From that starting point the calculator race created every year new integrated circuits with higher complexity following the Law of Moore. Working at another supplier of integrated circuits, the well known company Intel, Moore stated: Every three years the complexity of integrated circuits will double. The law is proofen, within 30 years the complexity reached more than a million of transistors per integrated circuit. 

In the meantime Texas Instruments stopped the production of integrated circuits for calculators. Most modern TI products use chips from Toshiba. View the calculator chips manufactured by Toshiba here.

It's difficult to get information about the calculator circuits manufactured by Texas Instruments. The following table gives an overview of the known circuits, a brief description and the calculators using them. 

First TI chip set produced for Canon Inc.

This set of 3 integrated circuits was streamlined to the Pocketronic with it's thermal printer. 
These chips are manufactured in a "state of the art" 10-micron 1-metal PMOS process and using Dual-Inline-Ceramic or Plastic (DIC/DIP) cases with 40 pins.

Second TI chip set produced for Canon Inc.

The second chip set supported displays instead the thermal printer of the Pocketronic. Two different Data Chips are known, the Arithmetic Chip was later replaced.
These chips are manufactured in a "state of the art" 10-micron 1-metal PMOS process and using Dual-Inline-Ceramic or Plastic (DIC/DIP) cases with 40 pins and 28 pins.

Third TI chip set produced for Canon Inc.

This chip set consists of 6 integrated circuit, one of them was later replaced.
These chips are manufactured in a "state of the art" 10-micron 1-metal PMOS process and using Dual-Inline-Plastic (DIP) cases with 40 pins.

Forth TI chip set produced for Canon Inc.

Compared with the previous chip sets the trend goes toward single chip solutions. Both chips contain together 512*13-bit read-only program memory, a 19*16-bit random-access memory and support calculators with upto 14 digits display width.
These chips are manufactured in a "state of the art" 10-micron 1-metal PMOS process and using Dual-Inline- Plastic (DIP) cases with 40 pins.

First TI chip set produced for Sumlock-Compucorp

This huge chip set was developed by the engineers of Compucorp and produced by AMI. Later TI qualified as a second source to AMI. The chip set forms one of the first programmable calculators, the Compucorp 324G Scientist.

First TI chip set produced for Olivetti

This rare chip set was found in October 2010 by fellow collector Miguel from Argentina in an Olivetti Logos 270 desktop printing calculator. The keyboard of the calculator sports unusual [*=] [/=] [Q], [P], [R] keys and [S] and [T]memories.
These chips are manufactured in a "state of the art" 10-micron 1-metal PMOS process and using Dual-Inline- Plastic (DIP) cases with 28 pins (TMC1829) and 16 pins (TMC1827, TMC1828).

Second TI chip set produced for Olivetti

This rare chip set was found recently in an Olivetti 55 desktop printing calculator. The keyboard of the calculator sports additional [00][000] keys, unusual [*=] [/=] keys and a memory.
These chips are manufactured in a "state of the art" 10-micron 1-metal PMOS process and using Dual-Inline- Plastic (DIP) cases with 28 pins (TMC1876) and 16 pins (TMC1828, TMC1877).

First commercial available single chip calculator

The first commercial available "calculator-on-a-chip" was an MOS integrated circuit announced by TI in September 17, 1971. Find the original press release here. The chip containes 3520-bit read-only program memory, a 182-bit random-access memory and a decimal arithmetic logic unit as well as control, timing, and output decoders but no drivers for the display. This gives an overall complexity of roughly 5000 transistors. The typical supply voltage ot this chip is ±7.2 V at roughly 15 mA power consumption. 
These chips are manufactured in a "state of the art" 10-micron 1-metal PMOS process and using Dual-Inline- Plastic (DIP) cases with 28 pins.
It took about a year till the first copy of the original design appeared. US based company MOSTEK introduced the MK5020P December, 1972.

First commercial available single chip scientific calculator

The original single chip calculator was limited to basic calculators. The TMS0120 added to the 8 digit mantissa a two digit exponent display but still uses external display drivers.  

Later single chip calculators

There are some later single chip calculators using external drivers for the display. One calculator, the Exactra 20 used only digit drivers, the segment drivers of the calculators were connected directly to the display. The TMS0135 e.g. containes 8192-bit read-only program memory, a 256-bit random-access memory and a decimal arithmetic logic unit as well as control, timing, and output decoders and the segment drivers for the display. This gives an overall complexity of roughly 8800 transistors. 

Chip set for 12 digit calculators

One limitation of the 28-pin packages of the TMS01xx was the maximum number of 10 or 8+2 digits for the results. For desktop calculators Texas Instruments developed chip sets with two 40-pin integrated circuits.    

Chip set for scientifical calculators

With the TMC0501 building blocks Texas Instruments created a novel architecture for scalable scientific calculators. The architecture used minimum a 2 chip design with the Arithmetic chip and the SCOM (scanning read only memory) but was expandable to a maximum of 8 SCOM's, additional RAM as program memory for programmable calculators, additional RAM for general purpose registers and even a chip driving a printer. Most scientific and programmable calculators from Texas Instruments between the years 1974 and 1982 (SR-50..TI-59) use these chips.
 
Abbreviations:

• ARITH     Arithmetic chip with 5*16 digits registers, segment scanning and driving
• SCOM     Scanning and Read Only Memory with 1k*13 instruction memory and 16*16 digits constants
• DSCOM   SCOM with doubled memory capacity of 2.5k*13 instruction memory and 16*16 digits constants
• QSCOM   SCOM with fourfold memory capacity
• BROM     Bare Read Only Memory with 1k*13 instruction memory
• DRAM     External Random Access Memory for user data (memory registers)
• PRAM     External Random Access Memory for user programms (key codes) with 1920 bits of read/write memory
• PROM     External Read Only Memory for user programms (key codes)
• PCHIP     Printer chip

Texas Instruments used the leading designation TMS (Texas Mos Standard) or TMC (Texas Mos Custom) for most chips. The following table uses only the (more common) TMC designations.

The TI-58/59 architecture introduced the Solid State Software Modules™ with up to 5000 program steps. On the backside of the TI-58/59 you'll note a small lid with a place for the 8-pin module, view it here.

Second generation single chip calculators 

There are some later single chip calculators using external drivers for the display. They support either a memory or some enhanced scientifical functions.

Third generation single chip calculators 

With the TMS1001 Texas Instruments introduced the first member of the famous TMS1000 Microcomputer family. The chip contains a microcomputer complete with a program ROM having 1,024 eight-bit words; a temporary storage RAM: input (from keypad); output (to control keypad scan and LED display); and an oscillator (clock). The TMS1000 chip was designed to span a range of hand-held calculator products (from four-function up through simple memory calculators). Since the chip had to be customized with the ROM program appropriate to a product, other programmable features were included to improve the chip's flexibility. Today we know 13 different chips used in TI single-chip calculators. These chips vary in implementation technology, number of I/O lines, display drive, amount of ROM (up to 26.6 Kbit) and amount of RAM (up to 1280 bits). Calculator applications range from simple four-function calculators to the 50-step programmable TI-57. As of mid 1979, over 35 million TMS 1000 chips were used in both calculator and noncalculator applications, establishing the TMS1000 as the computerarchitecture with the largest installed base. The internal clock rate varies from 200 to 450 KHz, depending on technology.

With the TI-1200 and TI-1250 calculators Texas Instruments introduced March, 1975 the first calculators using a real single chip design. The 8 digit LED-display and 8*4 matrix keyboard are connected directly to the integrated circuit and the whole system is powered by a single 9V battery.

Shortly before the introduction of the C-MOS technology in the year 1978 some chip-size optimized architectures appeared. Find more details in the description of the TMS1000 Microcomputer family. 

In the year 1976, with the SR-40 and TI-30 the first scientifical calculators using a real single chip design were introduced. These calculators used a 8 digit LED-display, too. In 1977 the display size was expanded to 8+2 digits.

The derivates were either numbered like TMC0271, TMC0272... or got a CD (Custom Design) number, e.g. CD2702.

First generation C-MOS single chip calculators 

In 1978 Texas Instruments introduced the first C-MOS calculator chips based on the TMS1000 Microcomputer family. The TP0320 architecture is similar to the TMC0980 chips introduced two years earlier for the TI-30 calculator. The main difference – beside the manufacturing process – is the permanent connection of the internal memory (64*13 bits RAM) to the supply voltage. This feature allowed the „Constant Memory“ found on the calculators based on the TP0320 family like the TI-50 or TI-53. Even after you turn off the calculator its user memory is stored inside the chip. The supply current is low enough to buffer the memory more than a year from two small button cells. The program memory with 2k*9 bits ROM allowed the conversion of most calculating features known from Majestic calculators (Scientifical, Statistical and Financial calculator or even Flight computers).

Remember that the first LCD-calculators sold by Texas Instruments used foreign calculator chips manufactured by Toshiba. Get more information about them here.

Together with the C-MOS process the employees of Texas Instruments changed the nomenclature of the chips. Instead of the leading characters TMS (Texas Mos Standard) or TMC (Texas Mos Custom) the abbreviation TP appeared for the new device families. These Microcomputers got both ROM programmability and Gate programmability (e.g. segment decoder). The derivates were either numbered like TP0320, TP0321... or got a CD (Custom Design) number, e.g. CD3202.

Simplified C-MOS single chip calculators 

During the calculator war (about 1976 to 1978) a lot of customized chip architectures apperaed even from Texas Instruments. Instead using the TMS1000 device with the large ROM and RAM amount some „area optimized“ architectures appeared. Don’t forget that in the early days of IC-Technology the yield of designs with some thousands of transistors was poor ! The TP0310 introduced in the year 1978 based on the serial architecture of the TMS0920 optimized for the TMS1050 calculator. This was the most compact design with only 511*9 bits ROM and 40*5 bits RAM using a one-bit serial adder. Only few calculators make use of the TP0310 devices.

Enhanced C-MOS calculator chips 

The TP0320 architecture with only 28 pin housings, 2k*9 bits ROM and 64*13 bits RAM limited calculator designs to simple Scientifical (TI-50), Statistical (TI-35) and Financial (Business Analyst II) calculators driving displays with only 8 digits (or 5 digits + 2 exponents) resolution. The "programmable" TI-53 stored as much as 32 key entries in the memory, that’s it!

Texas Instruments introduced with the TP0455 architecture a new design to overcome these limitations. It is still based on the TMS1000 architecture but added time-keeping capabilities and a more flexible display driver. The TP0455 is still gate-programmable. The first use of the TP0455 was the CD4501 design found in the Time Card introduced end of the year 1981. The TI-55 II demostrated the flexibilty of the TP0455 architecture, two chips formed a powerful Master-Slave architecture. The Master uses a 40pin housing and scans the keyboard, drives a huge display with 8+2 digits and performs the math capabilities. The Slave in the well known 28pin housing doubles the memory capacity of the calculator. This allows e.g. 56 programm steps compared to the 32 steps of the TI-53. The TP0455 design was soon replaced with the TP0456 and most designs were converted. The CD numbers were incremented 50 units to distinguish the difference between TP0455 (e.g. CD4515) and TP0456 e.g. CD4565). The TP0456 seems to be upward compatible to the TP0320, we know with the TI-30LCD resp- TI-30-II a calculator using either the CD3202 or CD4565 design.

We assume that the CD46xx nomenclature was used for original TP0456 designs, they were discovered mainly in educational toys.

The next step in the enhanced C-MOS architectures could be found in the TP0458 architecture. These chips with the CD48xx nameplate use always a 40pin housing and hold twice the RAM amount compared to the TP0456. In conjunction with the Master-Slave architecture some powerful calculators like the TI-62 Galaxy or TI-65 appeared with as much as 112 programming steps or 16 data memories and even timer functions. Single chip designs were discovered in „display intensive“ products like the TI-30 Galaxy or the rare BA-III.

With the introduction of the TP0458 we could close the history of calculator chips manufactured by Texas Instruments. The years between 1967 and 1982 brought us a lot of exciting calculator architectures driven by

• Technology (early steps with multi-chip designs)
• Flexibility (TMS1000 architecture)
• Cost Price (serial architectures)
• Development Costs (TP0456 architecture)

Failed C-MOS single chip calculators 

If you dig deep into the calculator related patents filed by Texas Instruments and know about the mystery TI-88 calculator you’ll discover two additional devices:

• TP0485 with CD2901,CD2902 and CD2903
• TP0530, TP0531 and TP0532 with CD5402 and CD5403

Unfortunately we don’t know much about them. The patent application is centered around a „Data processing system integrated circuit having modular memory add-on capacity“ and describes a TMS1000 chip with different slice-lines to produce area-otimized chips with adoptable memory size. According to the patent the ROM-size varies between 1k words and 4k words, the RAM-size seems to be between 56 and 224 bytes.

The inside view of a TI-88 gives you some chips but without destroying the calculator we aren’t able to reengineer it. One question is still open: Where are the 960 programming steps of a TI-88 stored ? It’s a pity that the TI-88 never got the final approval for production...

Display drivers

Before the real single-chip calculators appeared the LED displays were connected to digit drivers and on the first designs to additional segment drivers. 

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

© Juergen Dobrinski and Joerg Woerner, January 13, 2001. No reprints without written permission.