GB797912A - Digital information storage devices - Google Patents

Abstract

797,912. Electric digital-data-storage apparatus. NATIONAL RESEARCH DEVELOPMENT CORPORATION. March 21, 1957 [March 21, 1956], No. 8826/56. Class 106 (1). A digital information storage device includes a main store with a capacity of one major cycle and a subsidiary store with a capacity of one word, each store having a normally operative separate circulation path and the two stores having a common circulation path which is not normally operative, switching means for rendering the separate circulation paths inoperative and for rendering the common circulation path operative and an input path, whereby words incident at the input path of the said digital information storage device at corresponding instants of successive major cycles are stored in consecutive positions in the store. A long delay-line L, Fig. 2, holds eight words in minor cycles 0-7 and a short delay-line N holds one word. The contents of L circulate via the gates 14 and 16 and the contents of N circulate via the gates 18 and 20. For reading, the delay-line L is operated as a source by applying a pulse S to the gate 22 and for writing is operated as a destination by applying a pulse D to the buffer 42 whereby a copy of any word on the destination highway enters the line L via the gate 24, part of the contents of L being destroyed at the gate 16 to make room for the new information. If a pulse is on D during minor cycle 7 then gate 26 operates to cause entry of a word into N as well as into L. During any other minor cycle a pulse on PD puts on the trigger T which stays on until the end of the major cycle when it is put off by the pulse MC7, operation of the trigger T modifying the normal circulations of L and N by inhibiting the gates 14 and 18 so that the two delay lines have a common circulation via gates 34 and 36. During minor cycle 7 in the absence of a fresh word entry the contexts of N flow into L and also back into N via the gate 18 and the word then flowing out of L is destroyed at the gates 14 and 34. To extract a word from the store, a pulse PS is applied at the corresponding minor cycle and a copy of the word in the last minor cycle of the major cycle goes from N to the source highway via the gate 40. The circulations of N and L are modified by the trigger T in a similar manner to that of the reading operation. The PS and PD pulses may be applied for several consecutive minor cycles to read or write more than one word. The notation explained in Specification 717,114, which is referred to, is used in the drawings.