wdbm / MK-52

ELEKTRONIKA MK-52 MICROCALCULATOR

Will Breaden Madden

Introduction

The Elektronika MK-52 is an RPN programmable microcalculator. The MK-52 is one of the most advanced Soviet calculators ever made. The MK-52 was used as a backup for onboard computers of the Soyuz spacecraft mission TM-7 (1988-11-26--1989-04-27) for calculating the docking parameters of Soyuz docking with the Mir space station.

The MK-52 vacuum fluorescent display is quite dim and it is a very slow calculator, but it provides a powerful set of programming functions. The MK-52 is functionally identical to the MK-62, but features an internal non-volatile EEPROM memory module and expansion ports. One of the specific features of the B3-34 -- MK-54 line was a variety of undocumented features, substantially exceeding that of documented features. Some characteristics of the MK-52 as as follows:

characteristic	details
type	scientific
precision	8 BCD digits, exponent ±99
input mode	Reverse Polish Notation
production	Kiev, 1983--1991-11
price	115₽
volatile memory capacity	105
non-volatile memory capacity	512 kb
non-volatile memory type	EEPROM
clock speed	455 kHz ceramic resonator
ROM memory modules' type	fabric
size	212 mm * 78 mm * 35 mm
weight	250 g
display size	8 digit manissa, two digit exponent, separate signs
display type	green vacuum fluorescent
power supply unit	D2-37

Notation

Throughout this documentation, keyboard-key-style boxed characters represent microcalculator keys. For example, + represents the addition key.

Some key notations

key notation	key appearance
CHS	/-/
EE	Бл
enter	B↑
Addr	A↑
R/W	↑↓
R/S	C/л

switch notation	switch appearance
clear/read/write	C/З/CЧ
degrees/gradiants/radians	Р/ГРД/Г
data/programming	Д/P
automatic/programming	A/П

Modes of operation

The MK-52 has two main operating modes: automatic mode and programming mode. General calculations and operations are performed in automatic mode; programs are input in programming mode. To switch between modes, one must execute F /-/ to switch to automatic mode and one must execute F EE to switch to programming mode.

Automatic mode

Basic operations in automatic mode are conducted in accordance with RPN (Reverse Polish Notation) logic. For example, to evaluate 2+3, the following execution is required:

2 B↑ 3 +.

Programming mode

In simple programming, commands are typed into the MK-52 in programming mode and are then executed in order. The MK-52 is fully capable of memory management and both conditional and unconditional branching.

In programming mode, the screen displays information about the program in memory. For example, if

10 01 0E 03

is displayed, then this means that

• 0E is stored at program step 00,
• 01 is stored at program step 01,
• 10 is stored at program step 02

and the MK-52 is prompting for data to be input for program step 03. Individual program operations are represented by two-digit operation codes in programming mode.

10 01 0E 03

Memory

The internal volatile memory of the MK-52 has 105 steps. The internal non-volatile EEPROM memory is organised as 1024 4 bit nibbles and can store programs and data. Each program step requires 1 byte (2 nibbles) of memory; each register requires 7 bytes (14 nibbles).

Writing to non-volatile memory

Before entering a program into volatile memory with the intention of writing this program to non-volatile memory, the non-volatile program space to which the program is to be written must be cleared first, because performing the clearing operation clears the volatile memory as well as the selected area of the non-volatile memory.

Each program step requires 1 byte of memory and each register requires 7 bytes of memory.

When clearing, reading or writing to the non-volatile memory, the "address" and "range" are specified in the form of a six-digit number, preceded by a non-zero number (which is ignored) in automatic mode; i.e., 1aaaadd corresponds to dd bytes, starting at memory address aaaa. A two-position data/program switch (Д/P) controls whether data (from the registers) or program memory is transferred; a three-position switch is used to select clear, read and write operations (C/З/CЧ).

Example: Entry of program, writing to and reading from non-volatile memory

This example demonstrates the entry of a program (which simply adds 1 to a user input number and then displays the result) and the writing and reading of this program to and from non-volatile memory. The program is four steps long and, hence, requires 4 bytes of EEPROM memory.

• [Step 1] Clear the memory.
  • Switch the C/З/CЧ switch to C (clear) and switch the Д/P switch to P (program mode).
  • Switch the A/П switch to A (automatic mode).
  • Enter 1000004 (4 bytes starting at address 0000).
  • A↑ (address)
  • ↑↓ (R/W)
• [Step 2] Enter the program.
  • Switch the C/З/CЧ switch to CЧ (write).
  • Switch the Д/P switch to P (program mode).
  • Enter the program.
    • Initially, the screen should display 00, prompting for input.
    • B↑ (enter)
    • 1
    • +
    • The screen should display now 10 01 0E 03.
    • C/л (R/S)
    • The screen should display now 50 10 01 04.
    • The program is in volatile memory.