DE1574499

1,201,432. Electric digital data storage. INTERNATIONAL BUSINESS MACHINES CORP. 15 Jan., 1968 [16 Jan., 19671, No. 2109/68. Heading G4C. An electric digital data storage system comprises a circulating loop data store and a shift register arranged to execute serial data transfer to and from the loop and to execute parallel data transfer to and from the system, wherein the data circulating in the loop contains a control field the contents of which are sensed and used to determine the time to stop a data transfer from the loop to the shift register or the time to start a data transfer from the shift register to the loop. A central processor and a peripheral device communicate in both directions via a buffer including a delay line (magnetostrictive, or magnetic drum). The delay line can hold a 15- bit data field and 5 control bits. In general not all of the data field is occupied, the position of the end of the occupied portion being specified by the control bits which also specify when transfer with the processor is possible. The bits from the delay line output are gated into respective flip-flops in a "base register" then serialized by gates and passed via a shift register in a "base write control" block back to the delay line input. Bits from the peripheral device can be appended to the end of the circulating bit stream or bits can be passed to the peripheral device from the beginning of the stream, serially by bit in each case, part of the shift register in these cases being, by-passed by the circulating bits to shift them along, the control bits being up-dated. The delay line output is also shifted into a second shift register at the right time as determined by the control bits. The second shift register can receive data from or send data to the processor, parallel by bit. The second shift register can also supply data serial by bit to the delay line input via the shift register in the "base write control" block, a tag bit 1 being inserted in the second shift register after the last bit and shift out being terminated when the tag bit reaches the last stage (by detection of the pattern 00 ... 001). The system can handle several different byte lengths.