"Iskra-1250" calculator core rope memory

Long-term core rope memory unit of the programmable electronic engineering calculator Iskra 1250. Each calculator contained two such units. Unit is two printed circuit boards connected between themselves with an hinge. On the ends of each board there are connectors, with which the unit was inserted into plugs. On one of the boards there are memory elements and auxiliary parts, on the other there is a decoder in the form of a diode matrix.

Internal structure and specifications

The memory capacity is 4096 bytes. The board contains 128 memory cells, consisting of a memory transformer and an output diode. All storage transformers form a numerical matrix of 8 horizontal and 16 vertical rows, and every 8 transformers are made in a single case - a cell of the core block. It is made from HM-1500 type soft magnetic material and structurally consists of two parts - a holder and a yoke. The yoke is the upper removable part of the core block. It fits snugly into the cage by means of two springs and bolts holding them. The clip is the lower part. It consists of a housing with storage transformers inside. (in the form of pins, two rows of four, eight in total), around which a code wire is laid.

The memory element is a multi-winding transformer. The information is recorded by sequentially flashing the storage transformers with code wires - the primary windings of the storage transformers. When polling signals are applied to the winding, a signal of positive or negative polarity (logical zero or one) appears on the secondary winding, depending on the direction of the firmware (wire laying) of the primary winding. If the wire is laid around the transformer pin in a half turn, then a logical zero is written, and if in a full turn, then a logical one.

The diode decoder is located on the adjacent printed circuit board and consists of 256 diodes. A thin code wire leaves each, connects into a bundle and follows to the memory elements. One code wire sequentially bypasses all storage cells, which provides storage of 4 KB of data.

Additional information

Developed by Leningrad State Union Design and Technological Bureau for Production Counting Machines. Maked in 1981.

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