Texas Instruments SR-22

Date of introduction:  Sept.11, 1973 Display technology:  Panaplex II
New price:  $350 Display size:  10+2
Size:  9.1" x 6.5" x 2.6"
 232 x 165 x 67 mm3
Weight:  31.0 ounces, 881 grams Serial No:  5601
Batteries:  BP-200 Date of manufacture:  year 1974
AC-Adapter:  AC9222 Origin of manufacture:  USA
Precision:  13 Integrated circuits:  TMS0207, TMC0323, TMC0404
Program steps:   Courtesy of:  Joerg Woerner
    Download manual:   (US: 1.8M Bytes)

Look carefully at the display of the SR-22 and you'll notice immediately that this calculator could perform amazing calculations. It is the only calculator reported so far to perform Octal-Decimal-Hexadecimal conversions on the base of floating point numbers. Later calculators like the TI Programmer work only on integer numbers.

The SR-22 is one of the few scientific desktop calculators manufactured by Texas Instruments. It uses a housing with the size of a TI-3500 but the extreme wedge shape of the SR-10

Dismantling this SR-22 manufactured early in 1975 reveals a very rigid construction based on one rather complex printed circuit board (PCB) with two satellites:

The Panaplex II display manufactured by Burroughs.
The keyboard assembly with the keys, slider switch and discrete LED's.

The Main-PCB itself consists of four major building blocks:

Upper part Discrete high-voltage drivers for the Panaplex II display.
Middle-left Clock circuit
Lower-left Voltage supply
Middle-right Calculating circuit

The calculating circuit is formed by an impressive trio of 40-pin Integrated Circuits based on the TMS0200 Chipset for 12-digit desktop calculators introduced in 1973 for products like the TI-4000 and TI-450. Most of the known designs use only two chips, the TMS0200 Data Chip and the TMS0300 ROM Chip. Only this SR-22 and the massive TI-620 are known as of today using the TMC0400 ROM/Register Chip to double the program capacity from 512*13 Bits to 1k*13 Bits and adding two extra 16-digit Registers to the four Registers incorporated in the TMS0200 Data Chip.

The same housing was used with the simpler SR-20 calculator, while the huge power supply AC9222 was exclusively designed for the SR-22.

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If you have additions to the above article please email:

Joerg Woerner, December 5, 2001. No reprints without written permission.