EMG 666 calculator

• Data processing
• Technical and scientific calculations
• Measurement data collection

Structure

Central unit

Word-organized machine, 32 bpW

• controller: built from TTL and MOS LSI elements
  • program counter (PC) and instruction register
  • 2 index registers
  • universal rail system and
  • priority interrupt handling logic

• main store:
  • 1 KB RAM (112 data registers or 832 instructions)
  • 8 KB RAM (1008 data registers or 8000 instructions)
  • 2 KW ferrite ring ROM
• calculator:
  • 3 adatregiszter (X, Y, Z)
  • floating point decimal operation circuits
• channel: bus interfaces

Periphery

• backup storage: built-in cassette recorder (60 Bps)
• external devices:
  • 88-key keyboard for data and command input + 4 mode switches
  • CRT display (120*90 mm)
  • optional narrow matrix printer

Power supply: mains or battery (130 W)

Operation

The machine could be programmed with pushbuttons ("button language"), by calling the built-in (>200) or previously defined (≤ 20) own functions.

The microprogrammed instruction set (firmware) was contained in the ROM memory. Instruction types:

• Control instructions: conditional and conditional jumps, looping, recursive subroutine calls up to 8 times deep
• Data transfer between data registers and main memory, using direct or (chained) indirect addressing; data saving/loading to/from magnetic tape
• Calculation operations: basic operations, logarithm, squaring/square root, exponential and trigonometric functions

Data traffic was carried out directly on the data buses or via up to 15 transceivers (in bidirectional parallel — byte or bit-serial — “handshake” mode).

Data formats:

• 12 decimal (BCD) digit number representation
  • floating point mode
  • signed absolute value (value set: 1.0×10 ^-100 ÷ 9.99999999999×10 ⁺⁹⁸ )
• byte and character strings

Operation times:

• addition, subtraction: 0.3–0.5 ms
• multiplication, division, squaring: 2–6 ms
• square root: approx. 30 ms
• exponential functions: approx. 40 ms
• logarithms: approx. 120 ms
• trigonometric functions, x ^y: 100–300 ms

Show results:

• the contents of the 3 data registers are in one line each
• displays in 4 lines:
  • address counter register
  • next instruction code
  • other additional (error, keystroke) signals

Program set

There were no

There were no

Historical curiosities

This was the first programmable calculator in the CEEC zone.

Until the release of the HP 9825 calculator, it was the only calculator with hardware interrupts.

Resources

Detailed description: EMG 666