Circuit Arrangement Comprising a Matrix-Shaped Memory Arrangement for Variably Adjustable Time Delay of Digital Signals

This application is related to application Ser. No. 831,791 filed Feb. 2, 1986 and application Ser. No. 828,512 filed Feb. 12, 1986.

1. Field of the Invention

The present invention relates to a circuit arrangement for variably adjustable time delay of digital signals comprising a matrix-shaped memory arrangement.

2. Description of the Prior Art

Facilities for providing defined time delays of digital data streams are frequently required in the field of digital signal processing, as well as in the field of communications technology. Defined time delays are employed, for example, for the compensation of transit times. Given a constant number of desired delay clocks, an arrangement comprising a shift register is generally available as a time delay device. When, however, the time delay is to be variably adjustable, then particular problems arise given the use of shift registers.

It is also known in the art to delay data streams using an arrangement composed of standard circuits and memory modules. In such an arrangement, the components of the data stream are deposited in a freely addressable memory. This memory is driven by a decoder which is, in turn, driven by one (or more) counters. The duration of the time delay is thereby established by the spacing of the counter reset pulses. Since the memory cells of such freely addressable memories can only read or write, respectively, per clock, the necessity thereby arises of either operating the memories with twice the clock rate or switching back and forth between two memory units in a multiplex mode. The first solution of this problem is the disadvantage that the maximum data clock frequency can only be half as high as the maximum memory cycle frequency. The latter requires involved logic circuits for address control and a required reordering of the data. Disadvantages also arise for integration of such a circuit arrangement because of the high space requirement of the required multiplexers and because of the extensive wiring required.

The object of the present invention, therefore, is to provide a circuit arrangement of the type initially set forth by way of which defined, variably adjustable time delays can be achieved in fine graduations, which arrangement may be realized as an integrated circuit, and which has a smaller space requirement and allows higher data rates when compared to the arrangements known in the art. In particular, the object of the invention is comprised in creating a circuit arrangement which is particularly suited for integration in metal-oxide-semiconductor (MOS) technology.

According to the invention, the above object is achieved by providing a circuit arrangement for variably adjustable time delay of digital signals, the circuit arrangement comprising a matrix-shaped memory arrangement and being particularly characterized by the following features. First, known three-transistor cells having overlapping write/read cycles are provided as storage elements of the memory arrangement. A clock-controlled, continuously steppable row selector is provided and operates on a cyclic circulation principle, but can be reset at any time. The row selector comprises two respective signal outputs per selection step which are offset in phase with respect to one another and which drive a respective write word line or read word line which are provided per row of the matrix.

Two separate bit lines are provided per column, namely a write bit line and a read bit line, these being respectively interconnected to all memory cells of a column.

A disconnectible storage inverting amplifier is provided per column. The input of the amplifier is connected to the read bit line of the column assigned thereto and the output thereof is connected by way of a gate, dependent on the switch status thereof, either to the write bit line of the same column or to a data output. In the latter switch state, a data input is connected to the write bit line of the same column.

The data input for the data signals to be delayed is connectible to all write bit lines by way of the aforementioned gate circuits individually assigned to the columns, whereby only one of the m gate circuits is activated by way of a column selector which is controlled by a clock which is formed from the carry of the last stage of the row selector.

A reset line is connected to the setting inputs of a first element of a row selector and of a first element of the column selector, to the reset input of the remaining elements of the row selector and the reset inputs of the remaining elements of the column selector, as well as to the reset input of a counter which counts the pulses of the input data clock.

Finally, a reset signal for the reset line is acquired from a logic element to which an external reset signal is supplied via a first input and an external reset signal is supplied via a second input from a comparator. The comparator receives signals by way of selection inputs which define the number of steps of the counter after whose execution the reset signal is generated.

Other objects, features and advantages of the invention, its organization, construction and operation will be best understood from the following detailed description, taken in conjunction with the accompanying drawings, on which:

FIG. 1 is a block circuit diagram of a circuit arrangement constructed in accordance with a preferred embodiment of the invention in which a row selector, a matrix-shaped memory arrangement, regenerator circuits, a clock control, gate circuits, a column selector, a delay time setting device and a reset arrangement are provided;

FIG. 2 is a pulse/time diagram for explaining the manner of operation of the circuit arrangement of FIG. 1;

FIG. 3 is a symbolic representation contained in FIG. 1 and an equivalent circuit diagram of a three-transistor memory cell which is employed n.times.m fold in the memory arrangement of FIG. 1;

FIG. 4 is a symbolic representation contained in FIG. 1 of a regenerator (amplifier) and the equivalent circuit diagram thereof, such as employed m-fold in the circuit arrangement of FIG. 1;

FIG. 5 is a symbolic representation employed in FIG. 1 for a row selector stage and the equivalent circuit diagram thereof, such stage being employed n-fold in the circuit arrangement of FIG. 1; and

FIG. 6 is a symbolic representation employed in FIG. 1 for a gate circuit, along with an equivalent circuit diagram thereof, the gate circuit being employed m-fold in the circuit arrangement of FIG. 1.

As already explained, FIG. 1 illustrates a preferred exemplary embodiment of a circuit arrangement for variably adjustable time delay of digital signals comprising a matrix-shaped memory arrangement in accordance with the invention.

The illustrated circuit arrangement contains a data input D.sub.i, a reset input Reset, a clock input .phi. which synchronizes a clock control .phi..sub.P, as well as a data output D.sub.o. A cyclically circulating row selector comprising stages P.sub.1 . . . P.sub.n is also provided, wherein the stages and row selector are interconnected, the first stage P.sub.1 having a setting input s and the remaining stages P.sub.2 . . . P.sub.n have respective reset inputs r connected to a reset line Reset. A respective signal output b is connected to a signal input a of the following stage, and a write word line ws and a read word line wl are respectively provided per stage. Known three-transistor memory cells having overlapping write/read cycles are provided as storage elements in the matrix-shaped memory arrangement (cf. FIG. 3). The continuously steppable row selector P.sub.1 . . . P.sub.n which is resettable at any time is clocked-controlled by an input data clock. Per selection step, namely per stage, it comprises two signal outputs offset phase relative to one another (namely the write word line ws and the read word line wl, respectively) which are provided per row of the matrix. Two separate bit lines (a write bit line bs and a read bit line bl) are provided per column in the memory arrangement, these being respectively interconnected to all memory cells of a column. A disconnectable storage inverting amplifier A.sub.1 . . . A.sub.m is also provided per column, the input i thereof being connected to the read bit line bl of the column assigned thereto and the output o thereof being connected via a gate T.sub.1 . . . T.sub.m (depending on the switch state thereof) either to the write bit line bs of the same column or to the data output. A data input is connected to the write bit line of the same column in this latter switch state. The data input for the data signal to be delayed is connectible to all write bit lines bs via the gates T.sub.1 . . . T.sub.m individually assigned to the columns, whereby only one of the m gate circuits is activated by a column selector R.sub.1 . . . R.sub.m. The column selector R.sub.1 . . . R.sub.m is controlled by a clock .phi..sub.R which is formed from the carry of the last stage P.sub.n of the row selector P.sub.1 . . . P.sub.n. A reset line Reset is connected to setting inputs a, s of a first stage P.sub.1 of the row selector and of a first element R.sub.1 of the column selector, to the reset input r of the remaining elements R.sub.2 . . . R.sub.m of the column selector, as well as to the reset input r of a counter Z which counts off the pulses of the input data clock. A reset signal for the reset line Reset is acquired from a logic element G to which an external reset signal is supplied via a first input and to which an internal reset signal is supplied via a second input from a comparator K which receives signals via selection inputs D.sub.1 . . . D.sub.x which define the number of steps of the counter Z after whose execution the Reset signal is generated. The interval between the reset pulses corresponds to the required delay time.

As already set forth, FIG. 2 is a pulse/time diagram for explaining the operating mode of the circuit arrangement of the invention.

In FIG. 2, line A shows the basic clock .phi. applied to the clock control. Auxiliary clocks derive therefrom for the control of the row selector (cf. FIG. 5), namely .phi..sub.M, .phi..sub.M', .phi..sub.S and .phi..sub.S are shown in lines B, C, D and E, respectively. Line F shows the phase relation of the input data stream with reference to the basic clock .phi.. Lines G and H show the output signals of the row selector, namely the read word signal wl and the write word signal ws. Lines I and J show a precharge signal and a hold signal, respectively, which are employed for the control of the regenerator (amplifier) circuits (cf. FIG. 4). Line K, finally, shows the phase relation of the required reset signal with respect to the basic clock .phi..

As mentioned above, FIG. 3 is a symbolic representation of a three-transistor memory cell along with its equivalent circuit, the principle of operation thereof being based on the fact that the information to be stored is dynamically stored at the gate of an MOS transistor (the middle of the three transistors). As indicated by the terminal designations, this known three-transistor memory cell is employed in a specific operating mode wherein separate bit lines are used for reading and writing (cf. FIG. 1), whereby the possibility arises of reading and writing in a single clock cycle, this advantageously leading to the desired saving of time.

As also mentioned above, FIG. 4 is an illustration of an amplifier or regenerator shown both symbolically and in an equivalent circuit diagram. The job of the regenerator is to amplify the read signal appearing attenuated on the read bit line bl assigned to its input i, amplifying the same to a standard level and emitting the amplified signal to the output o. The circuit of this regenerator contains a three-stage inverter arrangement comprising a regeneration path therein. The inverter arrangement is preceded by a switch (controlled by the hold signal) which disconnects the inverter arrangement from the input i whenever the read bit line is precharged for the next clock cycle and thereby retains the stored information. The precharging is thereby effected by a further switch controlled by the Precharge signal.

In accordance with an advantageous feature of the invention, the circuit arrangement shown in FIG. 1 can be multiply provided in accordance with the word width of the input data, whereby the word write line ws and the word read line wl, respectively, of these memory matrices are connected in parallel and are connected to a row selector P.sub.O . . . P.sub.n provided in common for the matrices. Further, the column selector which controls the gates can be arranged in common for these memory matrices.

Another feature of the invention is that the row selector P.sub.1 . . . P.sub.n are respectively composed of a shift register SR, of a logic block LB and of two output drivers ATR.sub.1 and ATR.sub.2 having outputs ws or wl, respectively per element of the row selector, and that the phase relations and pulse widths of the output signals in the outputs ws and wl are effected by corresponding logic combinations of three taps present in the shift register SR.

As mentioned above, FIG. 5 shows a row selector stage P. Two dynamic register stages which can be separated from one another or, respectively, from the signal input by switches controlled with the assistance of auxiliary clocks .phi.'.sub.M, .phi.'.sub.M ; .phi..sub.S, .phi..sub.S are provided in a shift register block SR. The auxiliary clocks .phi.'.sub.M and .phi.'.sub.M correspond to the auxiliary clocks .phi..sub.M and .phi..sub.M of FIG. 2. However, they represent result signals of a logic operation of the appertaining signal shown in FIG. 2 with the reset signal. This logic operation effects a closing of the switch at the input of the switch register block SR for the duration of the reset signal. Two logic elements are provided in a logic block LB, these logic elements combining the signals appearing at the point c, d, b with one another in accordance with the following relationships

The output signals ws and wl of the logic block LB are connected via inverting drivers to the write word line ws or, respectively, to the read word line of the appertaining row of the matrix-shaped memory arrangement. A respective reset signal r is provided for the stages P.sub.2 . . . P.sub.n of the row selector of FIG. 1. This is replaced at the stage P.sub.1 by a setting input s as indicated with broken lines in FIG. 5.

As already set forth above, FIG. 6 shows the structure of one of the m gate circuits T which provide the following functions:

where "z" is indifferent.

The column selector R.sub.1 . . . R.sub.2 is preferably realized as a series arrangement comprising static shift registers, whereby the shift registers are switched by a phase clock derived from the clock signal .phi..sub.R.

Based on its structure, a circuit arrangement constructed in accordance with the present invention is particularly suited for realization as a monolithically integrated MOS circuit.

Although I have described my invention by reference to a particular exemplary embodiment thereof, many changes and modifications of the invention may become apparent to those skilled in the art without departing from the spirit and scope of the invention. I therefore intend to include within the patent warranted hereon all such changes and modifications as may reasonably and properly be included within the scope of my contribution to the art.