Synchronous circuit

The interlock mechanism of EP/3 uses both asynchronous and synchronous signals to control the components. This demonstrates that ITL is suitable for describing both synchronous circuits and asynchronous circuits. In (Cau and Zedan 1997) explicit constructs for both synchronous and asynchronous communication have been defined. 

It is now common practice, for verification as well as for synthesis purposes, to take the deterministic Mealy finite state machine (FSM hereafter for short) as abstract model for clock-synchronized circuits described at the register transfer level. The model is based on the following hypotheses ... 

T.R. Shiple "Formal Analysis of Synchronous Circuits", PhD thesis, U.C. Berkeley, 19%... 

For our experiments we use sets of benchmarks universally known in the field of CAD (ISCAS 89 and ISCAS 89-addendum). These are large synchronous circuits whose characteristics are reported in the literature. Experimental results show that the overall method is particularly effective on large circuits. 

Example 4.02 Consider a more complex synchronous circuit which consists of a data register count, two multiplexers muxi and mux2, and three functional blocks represented by uninterpreted function symbols inc, dec, and eqz. The functions inc and dec take as their input count and produce an abstract output inc count) and dec count), respectively. The cross-term eqz takes as its abstract input count and produces a concrete output of sort bool. The transition relation R of this machine is as follows ... 

Bose, S. Fisher, A. L. (1989), Automatic verification of synchronous circuits using symbolic logic simulation and temporal logic, tn Proceedings of the IMEC-IFIP Workshop on Applied Formal Methods for Correct VLSI Design . 

As discussed earlier, the disposition of constraints ( C ) is a design management problem. A peerhood relationship between PVS and DDD must include a framework for enforcing conditions when appropriate. In the counter optimization just described, bisimulation is contingent on certain input behaviors, hence these conditions are inherited as constraints on any system employing the synchronization circuit. 

Miner, P. S. Johnson, S. D. (1996), Verification of an optimized fault-tolerant clock synchronization circuit, tn M. Sheeran S. Singh, eds, Designing Correct Circuits , Electronic Workshops in Computing, Springer-Verlag. 

Transition tables for asynchronous circuits can convey significant information more quickly by placing circles about the next states that are stable, unstable next states are uncircled. The output and feedback variables have been labeled Q to identify them as state variables. This identifies the transition table for the asynchronous circuit with the transition table of the synchronous circuit. There is usually at least one next state entry that is, the same as the current state in each row. If this were not true then that state would not be stable. The procedure for obtaining a transition table is summarized in Table 1.28. 

Most of the modern electronic systems are synchronous systems. The clock is a central pace setter in a synchronous system to step the desired system operations through various stages of the computation. Latches are often used to facilitate catching the output data at the end of each clock cycle. Figure 8.2 shows the typical synchronous circuit with random logic clusters as computational blocks and latches as pace setting devices. When there exist feedbacks, as shown in Fig. 8.2, the circuit is referred to as sequential circuit. 

FIGURE 8.2 A typical synchronous circuit with combinational logic clusters and latches. 

By limiting the design object to a synchronous circuit, it becomes possible to describe LSI hardware in a procedure similar to a software program. A software program usually consists of only one procedure, while hardware behavior consists of plural procedures which, having been made to perceive time in the same way, can communicate with each other. 

Charles C (2008) An implantable I-UWB transceiver architecture with power carrier synchronization. Circuits and Systems, 2008. IEEE International Symposium on ISCAS, 2008, pp. 1970-1973. 

The sensitivity list provides die trigger for the execution of the process. Any signal that could be read by the process, and hence affect its behaviour, should be included in the list (Box 5.8). However, when creating a synchronous circuit using a Wait statement (Box 5.6) ti e process is triggered solely by the signal in the VWit expression. A sensitivity list must not be used with a Walt statement. 

Synchronous-motor rotor frequency can be detected because the rotor field circuit is available. Special control schemes have been devised which take into account both speed and induced rotor current in providing locked-rotor and accelerating protection. 

The magnetic field rotates at a synchronous speed, so it should also rotate the rotor. But this is not so in an induction motor. During start-up, the rate of cutting of llux is the maximum and so is the induced e.m.f. in the rotor circuit. It diminishes with motor speed due to the reduced relative speed between the rotor and the stator flux. At a synchronous speed, there is no linkage of flux and thus no induced e.m.f. in the rotor circuit, consequently the torque developed is zero. 

This is a scheme introduced in the AVR circuit to adjust the reactive power (kVAr) of a machine during a parallel operation or when it is being used as a synchronous condenser. It prevents a reactive circulating current, l. ... 

If the field excitation is also lost, the generator will run as an induction motor again driving the primer mover as above. As an induction motor, it will now operate at less than the synchronous speed and cause slip frequency current and slip losses in the rotor circuit, which may overheat the rotor and damage it, see also Section. 1.3 and equation (1.9). A reverse power relay under such a condition will disconnect the generator from the mains and protect the machine. 

At this stage, an auto-synchronizing relay (Relay Code 25) is brought into the circuit. This relay is suitable for any size of a generating unit to be synchronized automatically with another unit or an infinite bus. The relay executes three basic functions ... 

Are there any circuits that are particularly noise-sensitive These include analog-to-digital and digital-to-analog converters, video monitors, etc. This may dictate that the supply has additional filtering or may need to be synchronized to the sensitive circuit. 

For those applications where high efficiency is important, synchronous rectification may be used on the higher current (power) outputs. Synchronous rectifier circuits are much more complicated than the passive 2-leaded rectifier circuits. These are power MOSFE B, which are utilized in the reverse conduction direction where the anti-parallel intrinsic diode conducts. The MOSFET is turned on whenever the rectifier is required to conduct, thus reducing the forward voltage drop to less than O.f V. Synchronous rectifiers can be used only when the diode current flows in the forward direction, that is in continuousmode forward converters. 

Figure 3-30 Common synchronous rectifier circuits (a) nonisolated (b) self-driven (c) transformer-coupled.

Some power supply control ICs have synchronization inputs for this purpose. For those ICs which have an oscillator, but not a synchronization pin, the circuit in Figure 3-55 can be used. The frequency on the IC must be set lower than the synchronization signal. The sync signal causes the oscillator to prematurely time-out. 

Power Supply Cookbook, Second Edition has been updated with the latest advances in the field of efficient power conversion. Efficiencies of between 80 to 95 percent are now possible using these new techniques. The major losses within the switching power supply and the modern techniques to reduce them are discussed at length. These include synchronous rectification, lossless snubbers, and active clamps. The information on methods of control, noise control, and optimum printed circuit board layout has also been updated. 

The supply system for the power plant auxiliaries, including the provision of supplies to any important drives and the provision of standby supply systems. The protection and synchronizing schemes applicable to the generator circuit. 

In this chapter, we present the principles of conventional Mossbauer spectrometers with radioactive isotopes as the light source Mossbauer experiments with synchrotron radiation are discussed in Chap. 9 including technical principles. Since complete spectrometers, suitable for virtually all the common isotopes, have been commercially available for many years, we refrain from presenting technical details like electronic circuits. We are concerned here with the functional components of a spectrometer, their interaction and synchronization, the different operation modes and proper tuning of the instrument. We discuss the properties of radioactive y-sources to understand the requirements of an efficient y-counting system, and finally we deal with sample preparation and the optimization of Mossbauer absorbers. For further reading on spectrometers and their technical details, we refer to the review articles [1-3]. 

---