DATA STORE

1,173,367. Circuits employing bi-stable magrietic elements; transistor bi-stable circuits. INTERNATIONAL BUSINESS MACHINES CORP. 11 May, 1967, No. 21920/67. Headings H3B and H3T. [Also in Division G4] A matrix store having bi-stable data storage elements coupled between word lines and sense lines is such that a signal on a sense line produced by interrogation of an element can be used to set any further element coupled to the same sense line and conditioned to respond, and when an element is so conditioned the propagation of the signal to elements further along the sense line is inhibited. Fig. 3 shows a single storage element at the intersection of a word line and a complementary pair of bit/sense lines. One of transistors T1, T2 is conducting to store a bit. For reading, the word line potential is raised, thus cutting-off that one of the transistors T3 corresponding to the conducting transistor T1 or T2, producing a pulse on the corresponding bit/sense line at the top of Fig. 3. For writing, a pulse is applied to that one of the bit/sense lines at the bottom of Fig. 3 corresponding to the complement of the bit value to be written, and the potential on the word line is lowered then raised to normal again. The pulse on the bit/sense line causes the corresponding transistor T4 to conduct. The transistor T1 or T2 corresponding to the other transistor T4 will conduct when the word line potential returns to normal. The lowering of the word line potential prevents the pulse arriving on one of the incoming bit/sense lines (bottom of Fig. 3) from passing along the outgoing bit/sense lines (top of Fig. 3), by disabling the transistors T3. Accordingly a word can be written either from external bit drivers or from another word position in the matrix, and the passage prevention feature of the previous sentence enables a plurality of words to be transferred simultaneously. A modification straightforwardly omits one of the pair of sense lines and the associated transistors T3, T4 &c. Transferring a word in true rather than complement form is also mentioned. Thin magnetic film stores are mentioned. Specification 1,119,357 is referred to for alternative storage elements.