Synchronous counters

Unlike asynchronous counters, in which the output change of one flip-flop is applied to the clock input and thus changes the state of a succeeding flip-flop, synchronous-counter flip-flop outputs set up the J and K inputs of succeeding flip-flops so that a common clock-signal can cause the proper count sequence to occur. 

A synchronous binary up-counter is illustrated in Figure 23.21A. Compare this counter with the asynchronous binary up-counter in Figure 23.19. Notice that the synchronous counter requires external gating whereas the asynchronous counter does not this is because the count sequence is generated by the external gates which set up the J and K inputs of each flip-flop. The timing chart in Figure 23.19B for the asynchronous binary counter can also be used for the synchronous counter. 

The question arises, why one would use the more complex synchronous counters rather than the simple asynchronous counters One important reason is that in asynchronous counters the various count sequences must ripple from one flip-flop to the next. This means that an incoming count on the first flip-flop, which will... 

Figure 23.21. Synchronous counters. From S. P. Perone and D. O. Jones, Digital Computers in Scientific Instrumentation, New York McGraw-Hill, 1973, by permission of the publisher. Copyright 1973 by McGraw-Hill, Inc.

Figure 9. The event graph and resulting circuit for a three-bit synchronous counter. The logic generated by the templates has been optimized by sequential ffansformations. ...

This is why an induction motor ceases to run at synchronous speed. The rotor, however, adjusts its speed, N such that the induced e.m.f. in the rotor conductors is Just enough to produce a torque that can counter-balance the mechanical load and the rotor losses, including frictional losses. The difference in the two speeds is known as slip. S, in r.p.m. and is expressed in terms of percentage of synchronous speed, i.e. 

Let s consider internal structure of the generator G. As it was mentioned above, in the simplest case it can be simple summary counter with fixed increment value (W). It is quite enough to produce suitable synchronization sequence, because the single requirement for that sequence is to have no repetition on a given length. Such generator can be described by the next recurrent expression ... 

Now let s consider the overlapping event of two synchronization sequences for both case of counter mode building. 

In the Counter mode the synchronization sequence has fixed known differential property and therefore the base block cipher is potentially vulnerable to differential cryptanalysis attack. 

The pitch direction, i. e., the direction of the angle of rotation of the thread. If the thread of the element runs counter to the direction of rotation of the screw shafts, one obtains a conveying element. If the thread runs synchronously with the screw shaft rotation direction, the screw element will have a backward-pumping effect (Fig. 12.4). 

At the end of this injection process (80-90% filled), the two pistons will hydraulically separate the mold from the nozzle. The missing amount of polymer is now added from the small cylinders, countering the phases in the mold and the different molten Section 5 of the plasticized plastic is moved back and forth two to three times over the theoretical weld lines. After completion of this mixing process the cylinders are synchronized (phase B) (Fig. 14.18). 

Here is a model for a parameterized N-bit binary up-down counter with synchronous preset and preclear controls. The counting is synchronized to the rising edge of a clock. 

Here is a model of a modulo-binary up-counter. This counter has only a synchronous preclear control and all transitions occur on the rising clock edge. 

For example, a binary count of 4 bll00 corresponds to a Gray count of 4 bl010. Here is a Verilog HDL model for a parameterized N-bit Gray up-counter with synchronous preclear. 

Molecules that are ionized by electron impact in the ion source are accelerated, sent through a conventional 90° magnetic sector analyzer, postaccelerated by a few thousand volts, and arrive at the electron multiplier detector. The output of the electron multiplier detector consists of pulses of about lO- coulomb per ion. The pulses are amplified and sent through a gated amplifier and an electronic switch which is synchronized with the beam chopper so that one of the ion counters records ions only when the beam chopper is open, the other only when the beam chopper is closed. The difference between the two ion counts represents the ion intensity contributed by the molecular beam, while the square root of the sum of the two ion counts is approximately equal to the standard deviation of the measurement and serves as a useful indicator of the quality of the data being obtained. 

Ito, Y. Cross-axis synchronous flow-through coil planet centrifuge free of rotary seals for preparative counter-current chromatography. Part I Apparatus and analysis of acceleration. Sep. Sci. Technol. 1987, 22, 1971. 

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