Patent GB-921245-A (GB)
Title: Improvements in or relating to electronic data processing equipment
IPC: G06F3/06
Filed: 1960-03-16
Abstract: 921,245. Magnetic tape data-storage apparatus. BURROUGHS CORPORATION. March 16, 1960 [March 23, 1959], No. 9280/60. Class 106 (1). Data is transferred between a computer memory (such as a magnetic core matrix) and a magnetic tape store in blocks of words of variable length, each block being prefaced by digits indicating the number of words in it. The arrangement shown in Figs. 1A and 1B is adapted for use with the computer described in Specification 889,290, some elements of which are repeated in the present drawings. Words each of ten binary-coded decimal digits are transferred into and out of memory matrix 12 via a buffer 16, addressing being effected by an address buffer 14. Instruction words are transferred by means not shown to a command register 18, of which part 20 holds an address in 12, part 22 the order controlling the type of data transfer, K10 and K1 preface digits indicating the number of words per block, and N the number of blocks to be transferred. The order decoder 26 produces an output signal on one of the lines 1-6 if transfer between tape and memory 12 is called for. Decimal digits are stored on the tape in parallel on four tracks, and a block end mark track and a clock track (head 44) are also provided. Tape transport is initiated by a flip-flop 32 when set by switch 28. Writing.-For writing on to tape one of the lines #1, #2 from 26 is energized to set flipflop 53 and open gate 90 so that information may be read out in serial-parallel mode from 16 by WP pulses derived from the tape clock track and applied through gate 96. The transfer of information from the address given by 20 to the buffer 16 is effected by an initiating pulse from 28 via read-write switch 56 and delay 58. There are two types of write instruction; if #1 is energized the preface digits (i.e. number of words per block) are taken from the command register, and if #2 is energized the preface digits come from memory 12. In each case these digits are transferred to a register 60, via gate 62 or 74. The preface digits and operands from 16 are then transferred to tape via " or " gate 76 using the WP pulses through gates 82 and 96, the signal being amplified at 86. A counter 98 receives the WP shift pulses applied to 16 and at the end of each word resets flip-flop 94 and counts up the address registered in 14 to enable the delayed end-ofword signal through 58 to read the next word into 16, 94 being then set through 104 and 92 to read it out and on to the tape. The endof-word pulse via gate 132 also counts down the contents of the register 60 and when it registers zero produces an end-of-block pulse for recording on the tape, and counts down the N digit in register 20, so that after the required number of blocks have been recorded a " stop tape " signal is passed to gate 108. Reading.-In reading from tape into memory matrix 12 either line #5 or #6 will be energized, the latter if preface digits from the tape are to be recorded in 12. The locating on the tape of a required address is carried out by means not shown. Data read out from the tape passes via amplifier 114 (gated by clock pulses) and RP pulses are generated by 116 (should the " forbidden " digit 15 be produced by 114 no RP pulse will occur, and since recording is in phase-modulation form using " no change to represent binary 1 blank tape produces no RP pulse). The initiating pulse from 28 now addresses memory 12 and the preface digits are transferred to the register 60, and if the #6 line is energized also to memory by the initiating pulse switching 94 (via gates 120 and 92) to enable RP pulses to shift it into 16. Subsequent words are transferred to memory since monostable flip-flop 84 opens 96 (via gate 92) after the preface digits, and 98 counts the words as above described to count down the register (via 130 and 132). The N register is also counted down as before. Overwriting.-If this is called for by a signal on line #3 or #4 the tape is moved to a selected tape address as in " Reading " above. The preface digits either from memory 12 (#4) or from the C-register 18 (#3) are compared with those on tape at this address in a comparison circuit 148, to ensure that overwriting on to tape is admissible; if it is the operation as is in " writing " above, otherwise the tape is stopped and an alarm given.