SR-52
The SR-52 is a programmable scientific / engineering calculator from Texas Instruments with a built-in magnetic card reader .
Chronological order
The SR-52 hit the US market on September 15, 1975, priced at $ 395. In Germany it initially cost DM 1199. Today, adjusted for purchasing power, this corresponds to an amount of $ 1,872 or EUR 1,605. It was built until 1977 and then replaced by the TI-59 .
It was considered the answer to the HP-65 and was Texas Instruments' first programmable pocket calculator. The built-in magnetic card reader makes the computer very heavy and over 4.5 centimeters thick; it is basically not possible to actually carry it with you in a jacket or trouser pocket.
Technical equipment and functions
With 224, the SR-52 has more programming steps than the HP-65 (100), similar to the HP-65, key entries cannot be combined with Texas Instruments (except for the 2nd key), so that the command "STO 0 1" in the SR-52 requires three program steps and a jump with GTO (goto) to a program line could branch to the second part of a command (for example to the address of the STO-0-1 command) in a faulty program.
Magnetic cards are used for permanent backup of the programs (and data) created by the user , each of which can be written on in two tracks. Each track takes up half of the memory, so that a large program requires swiping the magnetic card twice.
Ready-made applications from various areas (e.g. aviation, navigation, electrical engineering, statistics and also a collection of games) could be purchased programmed on magnetic cards.
R.A.M.
The main memory of the computer comprises 224 program steps plus officially 20 data memories. However, due to undocumented features, it is also possible to use program steps as data storage; There are also two undocumented memories with the addresses 98 and 99, which are also not cleared by the CM (Clear Memory) command.
Advanced users can write programs that are distributed over several memory cards and reload parts themselves during runtime.
Program memory
One program step corresponds to two nibbles or one byte of storage capacity.
Data storage
A numerical data memory (13 digits mantissa + 2 digits exponent + sign ) occupies 8 program steps, which corresponds to (8 bytes) or rather 16 nibbles, since the pocket calculator with its 4-bit CPU works in a nibble-oriented manner.
Since the program memory can be addressed directly via the data memory addresses 70-97, the number of data memories can be increased at the expense of program steps. In addition, it is at least theoretically possible to change the program itself by storing computational results in the program memory.
programming
The SR-52 is programmed simply by pressing the desired key functions in LRN mode. When the program is run, the computer processes the recorded list of keys pressed. The programs created by the user are usually started using keys A to E (and their second assignments 2nd - A 'to 2nd - E').
The SR-52 offers e.g. B. a start / stop function, counting loops , conditional jump commands , multiple nested subroutines , direct and indirect addressing of data memories or program steps, simple symbolic program marks ( labels ) and program control using simple binary flags .
Display in programming mode
The seven-segment display used cannot display letters. In the programming mode, the program steps are displayed as a two-digit code in addition to the three-digit program step number. The numeric code corresponds to the row and column position of the key pressed on the keyboard.
The numeric codes “00” to “09” correspond directly to the numeric keys 0 to 9 for easier readability.
To save program memory is u. a. the code for the second assignment (" 2nd -Function-Key") of the keys is used as the numerical value of the key position plus 5. Pressing the 2nd key therefore does not occupy an additional program step.
To make it easier to read this rather cryptic representation, the computer came with a transparent keyboard overlay with printed number codes.
Undocumented features
In addition to the additional memories already mentioned, the addresses 60-69 could be used to access the workstacks of the computer.
Number format and calculation accuracy
The internal number format is 12 decimal places in exponential representation with 2-digit exponents plus the respective sign. Of these, 10 digits of the mantissa with a two-digit exponent and the sign are displayed, which should make calculation inaccuracies due to rounding errors less noticeable, i.e. H. the calculator calculates with two digits more than it shows at the end.
variants
Shortly after the introduction of the SR-52, the SR-56 was presented, which offered only 100 program steps and did not have a magnetic card reader. The table model SR-60 had its own buttons for each function (no double assignment of the buttons), a built-in printer and memory that could be expanded to up to 1920 program steps and 100 data memories (480 program steps and 40 data memories in the undeveloped state). The SR-62A was fully equipped ex works.
Optional accessories
The optionally connectable thermal paper printer PC-100 enables not only the printout of calculation results but also the printout of programs with line-by-line listing of alphanumeric key and numeric code representation as well as the program-controlled or manual printout of up to 20 letters and / or digits per line. The printer was used almost unchanged in the successor TI-59.
Technical specifications
- CPU: TMC0501 - 4-bit CPU
- RAM: 2 × TMC0599 with 1920 bit (SR-56 1x, SR 60 5x, SR-60A 13x)
- Display: 10 + 2-digit red 7-segment LED display
- Power supply: via the supplied mains / charger or exchangeable NiCd battery (3.6 volts)
- Interfaces: 12-pin bit serial interface for the printer PC-100
- Storage media: Magnetic cards with 2-track recording
Trivia
The NATO top spy Rainer Rupp (camouflage name Topas) is said to have received from the GDR State Security Service a device called "Schnellgeber", which serves as a telephone modem. The case comes from an SR-52.
Web links
- http://www.rskey.org/gene/hpgene/ - site of a collector of HP and TI pocket calculators
- http://www.rskey.org/tidocs.htm - Manuals for various programmable computers from Texas Instruments
Individual evidence
- ↑ The SR-52 on datamath.org (Eng.)
- ↑ The amounts were determined with the template: Inflation and refer to the previous January.
- ↑ Schnellgeber - code converter device for Stasi agents on missions abroad. German Spy Museum, accessed on July 23, 2018 .