Patent GB-948599-A (GB)
Title: Random access data storage system
IPC: G06K17/00
Filed: 1962-11-15
Abstract: 948,599. Statistical apparatus; random access stores. NATIONAL CASH REGISTER CO. Nov. 15,1962 [Dec. 8,1961], No. 43254/62. Heading G4M. Relates to random-access storage devices of the general type disclosed in Specification 889,788 and is concerned primarily with circuitry for co-ordinating the operation of one or more such devices with the operation of other data processing apparatus, for example a computer. A given strip 10, Fig. 2 bearing magnetically recorded data, is releasable from a stack regardless of its position therein, a released strip passing transducers 60m, 60n one or more times before being returned to the stack through guide 80. Photo-electric position sensing devices 60i, 60j, 90 are provided for detecting the presence of a strip, device 90 serving merely to control the operation of a loading device 205. Control circuits. Each storage device, of which only one, M1, is shown in Fig. 4, includes a storage section 150, shown in detail in Fig. 2, and a control section 250. The computer is linked to each storage device by command leads J1-J10, information leads PO1-PO8 and PI1-PI8, and status leads S1-S7 and MIS8-MIS10. Leads MIS8-MIS10 are individual to a particular storage device, in this case M1, and are activated to indicate certain operational conditions of that device. The remaining leads are common to all the storage devices. Selection of storage device. A command J1 is transmitted to all the storage devices concurrently with selection signals on leads PO1-PO8 whereupon one of the storage devices responds, i e circuits are conditioned to receive further commands, and any other device which was previously in the selected condition is reset. The computer is informed that selection has taken place by means of status lead MIS8. Strip selection. One or other of commands J9, J10 is transmitted concurrently with signals e 1 -e 8  over leads PO1-PO8. In either case the selection signals are gated to operate the release mechanism of the selected storage device provided that a previously released strip has reached position sensing device 60i, Fig 2. If call strip command J9 is transmitted, a previous strip is allowed to remain on the capstan for one more revolution so that a further read or write operation may be performed on it. If drop strip command J10 is transmitted, the operation is the same as for J9, but no further read or write operation may be performed on the previous strip during its last recirculation on the capstan. When a strip is released, a 'busy' indication is given on status lead S3 until the strip passes sensing device 60i. The release of a strip also causes return gate 70, Fig.2 to be opened for returning the previous strip to the stack when that strip reaches position sensing device 60j. As soon as the newly released strip reaches 60i, the 'busy' indication on S3 is removed and a 'ready' indication on S4 is given. Interruption of computer programme. Each storage device waits for commands from the computer before carrying out an operation. Owing to the different speeds of operation of the computer and the storage devices it is desirable that the computer should be able to carry out other parts of its programme while waiting for a strip to be positioned with respect to the read and write heads 60n, 60m. Facilities are therefore provided for informing the computer when a strip is in the transducing position so that the computer may interrupt its programme at a convenient point to read or write data on the strip. When such operation is desired the command J2 is transmitted to a selected storage device, the operation being resetable by command J3. An indication that a storage device has been set for interrupt operation is given on M1S9, and an indication that a selected strip is ready for reading or writing when convenient for the computer, is given on S6 and also on M1S10. Read operation. Assuming that the computer is able to interrupt its programme while a strip is still in the reading position, a test command J4 is transmitted to check that the leading edge of the strip is still between 60i and 60j, and this is followed by read command J5 together with channel selection signals ch1-ch8 on leads OP1-OP8 to select the desired data channel on the strip. The data read is transmitted to the computer overleads IP1-IP8 until a halt command J7 is transmitted. Write operation. Similar to read operation, write command J6 is transmitted with ch1-ch8, and the data written is read immediately afterwards for transmission over IP1-IP8 so that a check can be performed in the computer. Return of strip to stack. As described above a strip is returned to the stack automatically when a new strip is released by J9 or J10. A separate return strip command J8 is also provided. Each storage device also has an automatic timer which ensures that a strip is not left on the capstan indefinitely. System operations. Illustrative examples of operations which may be performed by the system as a whole are given. In one, a bookkeeping operation is performed in which a card is released, a particular account balance is read, updated in the computer, and the new balance written in the appropriate place on the strip before returning it to the stack. Two examples are given of an operation using one or more storage devices in which an account number is read, compared with a reference number, and is then re-written in one or other of two files comprising strips in the same or different storage devices, according to whether the account number is smaller or larger than the reference number. Modified storage device, Fig. 14. A retractable stop member 671 is provided whereby a released strip 10 may be held just above the capstan until required. The member 671 may be actuated in response to further commands J11, J12. The guide 85<SP>1</SP> is provided with boosters 610 which may be similar to the capstan, whereby the speed of a strip in the guide may be maintained or accelerated. In this way strips may be transferred between storage devices, for example by means of gates 690.