Patent GB-985266-A (GB)
Title: Shifting register
IPC: G11C19/28
Filed: 1963-12-16
Abstract: 985,266. Shift registers. SPERRY RAND CORPORATION. Dec. 16, 1963 [Dec. 24, 1962], No. 49567/63. Heading G4C. [Also in Division H3] In a shift register,each stage comprises a tunnel diode, non-linear impedance means being connected between the input for the stage and coupling means connected to the tunnel diode, means responsive to the tunnel diode state being effective to control the non-linear impedance means thereby selectively decoupling the coupling means from the input in dependence on the tunnel diode state. As shown, Fig. 1, each shift register stage 100 comprises a tunnel diode 40 connected via coupling means in the form of a transformer T 2  to two ordinary diodes 24, 26 which are connected together to receive shift clock pulses from a terminal 38. The input to the stage 100 from the tunnel diode 16 of the previous stage is via an ordinary diode 22. Initially all the tunnel diodes are in the "low" state representing "O" and each shift pulse applied to terminals 38 &c. passes via both diodes 24, 26 to produce no resultant effect in the transformers T 2  &c. A high level, "1"- representing signal is applied from an input 10 to one half of the primary winding 12 of transformer T 1  thereby switching tunnel diode 16, current being provided via a backward diode 20. When tunnel diode 16 is in its "high" state, potential is applied via diode 22 to the cathode of diode 24 which is thus reverse biased so that when the next clock pulse is incident at terminal 38, current flows via diode 26 only thereby causing tunnel diode 40 to be switched via transformer T 2  after slight delay due to the R-C network 28, 30 and series inductance so that tunnel diode 68 in the next stage is not incorrectly switched at the same time. Tunnel diode 68 in the next stage will be switched in response to the next clock pulse and the "1" state is progressed down the register in a similar manner. When the input signal from the source 10 returns to a low level, tunnel diode 16 may be reset to its "low" state by a source 10a thereby unblocking diode 24, diode 26 remaining blocked in response to the "high" state of tunnel diode 40. The next clock pulse can therefore pass from terminal 38 via diode 24 to provide,via transformer T 2 ,a signal to switch tunnel diode 40 to its "low" state,this "low" state being then progressed along the register in response to successive clock pulses. Reversible shift register. A shift register, Fig. 3, in which each stage comprises a tunnel diode 106 and associated control circuit 104,the arrangement being similar to that of Fig. 1, is provided additionaly with a shift direction control circuit for each stage comprising tunnel diodes 114, 118 normally in a monostable operating condition. When the shift register tunnel diode 106 in the "high" state,the application of a signal to "shift left" terminal 128 or "shift right" terminal 126 causes the associated tunnel diode 114 or 118 to switch to the high voltage condition so that an output is provided via either diode 120 or diode 122 to the control circuit of the preceding or succeeding shift register stage respectively.