Abstract:
A circuit configuration for storing data has a first clocked register structure connected in parallel with a second register structure. The second register structure is operated in a push-pull mode relative to the first register structure. As a result, changes in the state of an input signal at the input are stored for each clock phase of a clock signal. Therefore, the clocking of the input signal of the circuit configuration can be done at the clock rate of the clock signal.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a circuit configuration for storing data, in which the data are written in and read out under clock control. 
     For storing data in the form of logic signals, particularly for brief buffer storage, it is well known to use registers. A register maintains its logic state until it is changed by a different logic signal or by special control commands. 
     The storage of the data can be done dynamically, for instance by changing the load state of a capacitor, or statically, for instance with a bistable multivibrator. 
     The transfer of data from the register is done usually at fixed times that are determined by a clock signal. The output of the register is released only in certain clock phases, for instance at a leading or trailing edge thereof. Complete decoupling of the input from the output of the register is obtained if the transfer of data to the register is also possible only at certain times fixed by the clock signal, and if the data transfer and entry take place at different times. The decoupling assures that a datum is not overwritten by a subsequent datum before it is read out. In principle, such a register includes a unit for storing a datum in memory, a clocked switch for transferring the data to the unit, and a clocked switch for takeover of the data from a precursor stage. At any time, the switches must assume different circuit states from one another. If one switch is opened, the other must be closed, and vice versa. 
     Relaying data from the input to the output of the register is made up of a transfer step, in which the data are transferred to the circuit, and a takeover step, in which the data are taken over by the circuit. 
     A disadvantage here is that a datum at the input of the register is not available at the output until after a period length. To store the data in memory without loss, the clock frequency of the clock signal must be twice as high as the frequency with which the data at the input of the register can change their state. In other words, changes in the state of the data can occur at only half the frequency of the clock signal. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a circuit configuration for data storage which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, in which a more-effective clock-controlled storage of data is provided. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit configuration, including: an input terminal; an output terminal; a first memory device for storing data connected between the input terminal and the output terminal; first means connected in series with the first memory device, the first means receiving a clock signal for disconnecting the input terminal from the output terminal; a second memory device; second means connected in series with the second memory device, the second memory device and the second means connected in parallel with the first memory device and the first means, the second means being clocked in a push-pull fashion with the first means. 
     The invention has the advantage that the frequency with which the data can change their contents is equal to the frequency of the clock signal. In the circuit configuration of the invention, input data are stored at each trailing edge and each leading edge of a clock signal. 
     It is also advantageous that the power consumption per storage cycle is virtually unchanged compared with known circuit configuration for data storage. 
     In accordance with an added feature of the invention, the first means have a first MOS transistor of a first conductivity type is disposed upstream of the first memory device and a second MOS transistor of a second conductivity type is disposed downstream of the first memory device, and the second means have a first MOS transistor of the second conductivity type is disposed upstream of the second memory device and a second MOS transistor of the first conductivity type is disposed downstream of the second memory device. 
     In accordance with another feature of the invention, at least one of the first memory device and the second memory device has a pair of anti-parallel-connected inverters. 
     In accordance with an additional feature of the invention, at least one of the first memory device and the second memory device has an output terminal and a storage capacitor connected between the output terminal and a reference potential. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a circuit configuration for data storage, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block circuit diagram of a circuit configuration according to the invention; 
     FIG. 2 is a block circuit diagram of an exemplary embodiment of a storage device; 
     FIG. 3 is a timing diagram; and 
     FIG. 4 is a circuit diagram of the circuit configuration. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a circuit configuration of the invention which has a first storage device M 1  and first means S 1 , S 2 . Connected parallel to the first storage device M 1  and the first means S 1 , S 2  are a second storage device M 2  and second means ST 1 , ST 2 . The first and second means S 1 , S 2 , ST 1 , ST 2  are each clock-controlled. The first means S 1 , S 2 , in accordance with FIG. 1, are embodied as a first switch S 1  upstream of the first storage device M 1  and a second switch S 2  downstream of the storage device M 1 . The switches S 1 , S 2  are each controlled by one clock signal Φ. For a certain clock signal, such as a logical 1, the switch S 1  is closed while the switch S 2  is open. 
     The second switching means ST 1  here includes a first parallel switch ST 1  upstream of the second storage device M 1  and a second parallel switch ST 2  downstream of the second storage device M 2 . The parallel switches ST 1 , ST 2  can also be supplied with the clock signal Φ. 
     At a certain time, the first parallel switch ST 1  assumes the same state as the second switch S 2 , while the second parallel switch ST 2  assumes the same state as the first switch SI. 
     A terminal of the first switch SI that is not connected to the first storage device M 1 , and a terminal of the first parallel switch ST 1  that is not connected to the second storage device M 2 , are connected to one another and form an input IN of the circuit configuration. A terminal of the second switch S 2  that is not connected to the first storage device M 1 , and a terminal of the second parallel switch ST 2  that is not connected to the second storage device M 2 , are connected to one another and form an output OUT of the circuit configuration. 
     In FIG. 2, the first storage device M 1  and the second storage device M 2  can each be constructed from one capacitor C, which is connected between a reference potential V ss  and an external terminal of the respective storage device M 1 , M 2 . The external terminal may be an input or an output terminal of the respective storage device M 1 , M 2 . In the first storage device M 1 , the connection of the capacitor C to the external terminal is configured as a node point K 1 , while in the second storage device M 2  it is designated as node point K 2 . 
     The mode of operation of the circuit configuration of the invention as shown in FIG. 1 will be explained below in terms of FIG.  3 . Without restricting the general applicability of the storage devices M 1 , M 2 , in each case, the embodiment having the storage capacitor C of FIG. 2 will be made the basis of the invention. The basic mode of operation of the circuit arrangement of the invention is not dependent on the embodiment of the storage devices M 1 , M 2 . 
     In the timing diagram of FIG. 3, the clock signal Φ, an arbitrarily selected input signal INS, a first memory signal MS 1  which here appears at the first node point K 1  of the storage device M 1 , a second memory signal MS 2  that appears here at the second node point K 2  of the storage device M 2 , and the output signal OUTS of the circuit configuration are plotted over time t. 
     It is assumed that for a logical zero of the clock signal Φ, the first switch S 1  and the second parallel switch ST 2  are closed, while the second switch S 2  and the first parallel switch ST 1  are open. For a logical one of the clock signal, the first switch S 1  and the second parallel switch ST 2  are open while the second switch S 2  and the first parallel switch ST 1  are closed. 
     It is also assumed that at the onset of observation, all the signals are logical zeros, for instance because of a reset. 
     While the clock signal Φ is logical 0, a leading edge of the input signal INS is reflected in the first memory signal MS 1 , after a brief delay dictated by the transit time of the signals. The second memory signal MS 2  does not assume the logical state of the input signal INS, that is, logical 1, until some delay after the clock signal Φ is logical 1. Upon the change of the clock signal Φ to logical 1, the second switch S 2  is closed, and the output signal OUTS, again with some delay, takes on the logical 1 of the memory signal MS 1 . 
     A trailing edge of the clock signal Φ following the leading edge remains at the first memory signal MS 1 , and the second memory signal MS 2  and the output signal OUTS remain without effect, as long as the input signal INS remains at logical 1. 
     A trailing edge of the input signal INS is taken over by the first memory signal MS 1  during the logical 0 of the clock signal Φ. The second memory signal MS 2  does not assume the logical 0 of the input signal until the logical 1 of the clock signal Φ. At approximately the same time, the output signal OUTS takes over the logical 0 of the first memory signal MS 1 . 
     Another change of the input signal INS to logical 1, while the clock signal Φ is logical 1, is taken over by the second memory signal MS 2 , merely with some delay. The takeover of the logical 1 of the input signal INS takes place, for the first memory signal MS 1 , only after a change of the clock signal Φ to logical 0. At approximately this time, however, the logical 1 of the second memory signal MS 2  is already relayed to the output signal OUTS. 
     A trailing edge of the input signal INS during a logical 0 of the clock signal Φ is taken over by the first memory signal MS 1  with a slight delay. For the second memory signal MS 2 , the takeover of the logical 0 occurs only after the change of the clock signal Φ to logical 1. At approximately that time, the change of the output signal OUTS to logical 0 takes place, in response to the trailing edge of the first memory signal MS 1 . 
     A change in the state of the input signal INS is accordingly taken over by the output signal OUTS at each pulse edge, that is, both the leading edge and the trailing edge. 
     One possible conversion of the basic circuit of FIG. 1 into a concrete circuit is shown in FIG.  4 . The exemplary embodiment of FIG. 4 has a first inverter INV 1 , which is connected on the input side to a first switching transistor SN 1  of a first conduction type and on an output side to a second switching transistor SP 1  of a second conduction type. Connected parallel to the first inverter INV 1  is a series circuit of a locking transistor VP of the second conduction type and a second inverter INV 2 . An output of the first inverter INV 1  is thus connected to an input of the second inverter INV 2 . Gate terminals of the first switching transistor SN 1  of the first conduction type, the locking transistor VP of the second conduction type, and the second switching transistor SP 1  of the second conduction type are connected to a terminal of the clock signal. 
     The exemplary embodiment of FIG. 4 further includes a third inverter INV 3 , which is connected on an input side to a third switching transistor SP 2  of the second conduction type and on an output side to a fourth switching transistor SN 2  of the first conduction type. Connected parallel to the third inverter INV 3  is a series circuit including a second locking transistor VN of the first conduction type and a fourth inverter INV 4 . The output of the third inverter INV 3  is thus connected to the input of the fourth inverter INV 4 . Gate terminals of the third switching transistor SP 2  of the second conduction type, the second locking transistor VN, and the fourth switching transistor SN 2  of the first conduction type are connected to a terminal of the clock signal Φ. 
     When the first locking transistor VP is conducting, the first inverter INV 1  and the second inverter INV 2  are connected anti-parallel. Analogously, the third inverter INV 3  and the fourth inverter INV 4  are connected anti-parallel, when the second locking transistor VN is conducting. 
     The channel side, remote from the first inverter INV 1 , of the first switching transistor SN 1  of the first conduction type and the channel side, remote from the third inverter INV 3 , of the third switching transistor SP 2  of the second conduction type are connected to the output of an input inverter EINV. On the input side, the input inverter EINV is connected to the input terminal IN of the circuit configuration. 
     A channel side, remote from the first inverter INV 1 , of the second switching transistor SP 1  of the second conduction type and the channel side, remote from the third inverter INV 3 , of the fourth switching transistor SN 2  of the first conduction type are connected to an input of a first output inverter AINV 1 . An output of the first output inverter AINV 1  is connected to an input of a second output inverter AINV 2  and is connected to the series circuit of a third and fourth output inverter AINV 3 , AINV 4 . The output of the second output inverter AINV 2  is connected to the output terminal OUT of the circuit configuration. The output of the fourth output inverter AINV 4 , connected downstream of the third output inverter AINV 3 , is connected to an inverting output /OUT. 
     Both the input inverter EINV and all of the output inverters serve to increase the driver power. For the basic mode of operation of the exemplary embodiment, they are not significant. The first inverter INV 1 , the second inverter INV 2 , and the locking transistor VP of the second conduction type form the storage device M 1 . The third inverter INV 3 , the fourth inverter INV 4 , and the locking transistor VN of the first conduction type form the storage device M 2 . 
     In FIG. 4, the first switching transistor SN 1  of the first conduction type is an n-channel transistor, and the third switching transistor SP 2  of the second conduction type is a p-channel transistor. At each logic state of the clock signal Φ, the input signal INS is therefore stored in one of the storage devices M 1 , M 2 , namely in the storage device M 2  at a logical 0 of the clock signal Φ and in the storage device M 1  at a logical 1 of the clock signal Φ. 
     At a logical 1 of the clock signal Φ, the first switching transistor SN 1  is opened, and the locking transistor VP of the second conduction type, in this case a p-channel transistor, is opened. The input signal INS is inverted by the first inverter INV 1  and delivered to the second inverter INV 2 . If the clock signal Φ changes to logical 0, then the locking transistor VP of the second conduction type is made conducting. Because of the positive feedback structure of the first and second inverter INV 1 , INV 2 , the logical state of the storage device M 1 , which prevailed before the locking transistor VP of the second conduction type was made conducting, is maintained. Since the first switching SN 1  transistor of the first conduction type is blocked at the logical 0 of the clock signal Φ, this state cannot be overwritten by the input signal INS during this clock phase. 
     The storage operation of the storage device M 2  proceeds analogously. 
     The invention has been described in terms of a register of a 1-phase type, that is, with a 1-phase clock control. However, it can readily be expanded to multiphase clock systems as well.