Электроника МК-52
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Микрокалькулятор Электроника МК-52
Elektronika Microcalculator MK-52
- Type: Programmable RPN Electronic Calculator
- Size: 8 x 2.5 x 1.5 inches / 21 x 8 x 4 cm
- Serial number: 008517
- Date of Manufacture: January 1991
With transparent hard case, manual in 2 volumes, and 220-volt AC adapter for European sockets.
The last true Soviet-technology calculator. After the fall of the Soviet Union, the member states went to Japanese knockoffs. I can't help but wonder what direction the Soviets would have taken in calculator technology had they survived.
Modern calculators use low-power CMOS memory to retain data (called "constant memory" when introduced). A number of calculators provided options for secondary storage. Magnetic strips were popular (TI-59, HP-65/95, HP-41) and the HP-41 could interface with a magnetic tape cartridge unit. Today, the HP-49g+ and HP50g provide a Secure Digital card slot for handy backups.
But while the West was playing with magnetic doohickeys, the Soviets came up with a solution of their own: EEPROM. Main memory was too hungry to keep powered up (and, truly, the Kvant A-316 cell at 400 mAH will never be confused with an Eveready). But an EEPROM needs no power to keep its marbles. So, the manufacturer came up with a way of letting you store your programs and data in the EEPROM before the power-off wiped main memory clean.
Two new keys were added, an "Address Enter" key and a "Read/Write" key that would execute whatever the "Clear/Write/Read" switch was set to. Another switch selected whether you stored program memory or register contents. There are two expansion ports, one with 16 pins and one with 22. Application ROMs were available, including a classified astronomical navigation package that was supplied to the Mir Space Station cosmonauts as a backup computer. Other than that (and the form factor) the calculator had the same features as the MK-61.
The unit was clearly intended for desktop use, with an ergonomic wedge shape and a transparent hard dust cover rather than a padded travel case.
But how does it work? Well, if ever you thought the Soviets were sneaky, this calculator will not disillusion you. I wrote a 32-byte program that I tried to store starting at EEPROM location 0. So, I set the Clear/Read/Write switch to Write ("З"), keyed 1000032, Address Enter, Read/Write, and voila! Every byte except byte number 28 was recorded. Every time I recalled the program to main memory, byte 28 was 00. Sigh. Did I have a bad unit?
Well, I was flipping through the manual, wishing I knew more than 6 words of Russian, when I found this big chart in the middle of volume 2. It seemed to be a conversion chart to help the programmer fit bytecode into a nybble-addressed EEPROM. It turns out that the memory isn't written in a linear manner. The 32 bytes I was writing included bytes 33 and 34, but not byte 28. Byte 28 of program memory is stored in byte 35 of the EEPROM. Oh well. It's documented, so it must be a feature!
(Helpful Hint: Store program steps in multiples of 7, rounding up when necessary. You have to do that when you store data registers; at least it'll be consistent. And you won't waste space by writing 98 bytes every time "just to make sure".)
Manufactured by Квасар (Quasar) Factory
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