Patent GB-1215168-A (GB)
Title: Test system for magnetic storage arrays
IPC: G11C29/50
Filed: 1968-10-18
Abstract: 1,215,168. Testing magnetic storage apparatus; semi-conductor circuits. INTERNATIONAL BUSINESS MACHINES CORP. 18 Oct., 1968 [15 Nov., 1967], No. 49452/68. Headings H3B and H3T. The cores of a three dimensional magnetic storage matrix 10, Fig. 1A, are switched sequentially under the control of a data processor 36, so as to produce, in turn, in a selected sense winding S1-S3 a first output pulse in respect of a stored "1", and a second output pulse in respect of a stored "O", the output pulses being applied through a sense amplifier 34 to a plurality of sampling channels 41-46, Fig. 1B, each of which is operative in a different time position within the time span of an output pulse. Each sampling channel produces a continuous output voltage between successive pulses which corresponds to an instantaneous value of the output pulse last sampled, and these voltages are passed to the processor 36 which indentifies any storage cores which fail to produce an output of a desired waveshape. The data processor 36 controls X, Y and Z addresses 15, 16, 17 each consisting of registers 18, 19, a decoder matrix 20, and gates 21 controlled by a driver 24. The X and Y addresses 15, 16 apply coincident half currents of appropriate polarity to a single row line X1-X3 and a single column line Y1-Y3 of the storage matrix W for writing or reading, while energization of all but one of the inhibit lines Z1-Z3 by the Z address 17 restricts writing to a single matrix plane. Read out is restricted to the plane containing the selected core by a sense line address 30 which closes a single switch 31-33 in the output path of sense lines S1-S3. The sense amplifier 34 includes transistor circuity 100, Fig. 3, equivalent to a double-pole double-throw switch, which is controlled by the data processor selectively applying a positive or negative potential through a line 149 to a circuit 148, the arrangement ensuring that the sense winding output pulses EA are always applied to the sampling channels with the same polarity. The output EA is applied through lines 49-53 to all the sampling channels in parallel and is delayed by the same amount within the channels by a delay 55. Each channel is controlled by a common clock 38 which produces a pulse at the commencement of each sense output pulse. A reference voltage E1, different for each channel and determining the sampling time, is applied to terminal 48. Each clock pulse operates a trigger 59 which starts a fast ramp generator 65. When the instantaneous ramp voltage equals the exclusive reference voltage E1 of the channel, a comparator 64 triggers a blocking oscillator 66 and so momentarily actuates gate driver circuits 67, 75. The output EA from the sense amplifier (on line 49) passes through a transformer 54 and the delay 55 to a sampling gate 68 which comprising a four-arm balanced diode bridge forwardly biased by the operative circuit 67. The unbalance signal is passed through amplifiers 69 and a memory gate 74 to an operational amplifier 71 providing feedback through a loop 77 to the sampling gate, the feedback voltage providing a reference voltage on the bridge for the next sense signal EA. The amplifier 71 includes a negative feedback capacitor 73 which maintains a charge equal to the reference voltage when gate 74 closes, this voltage being passed to the data processor through line 78. The double-pole double throw transistor circuitry 100, Fig. 3, for switching the polarity of the sense signal consists of four transistors of which either transistors 101, 103 or 102, 104 become conductive when a potential from circuit 148 is applied to functions 100a or 100b respectively. Circuit 148 is controlled by a pulse in line 149 the polarity of which depends on the input signal polarity at terminals 34a, 34b so that either transistor 150 or 151 become conductive. Thus the potential applied from circuit 100 to an emitter-follower pair 111 maintains the same polarity irrespective of the polarity of the input signal. The emmiter-follower output is distributed to the sampling channels through respective transistors 134-138 and coupling capacitors 144. A power supply at terminal 118 is smoothed by components 142, 143, 145, 146 and the switching transient produced by the circuit 100 is absorbed by capacitors 114, 115.