Asynchronous logic

The statements within each if branch (except the last) represents asynchronous logic, while the statement in the last else branch represents synchronous logic. 

The Process statement part may only contain sequential statements such as If-Else, Case and For Loop (Chapter 6). These are executed in the order in which they appear and the behaviour will be modelled with combinational and/ or sequential (synchronous or asynchronous) logic. 

The approach I developed is a purely logical, fully asynchronous one,... 

The versatile drive system of the asynchronous canned motor has set fresh yardsticks for centrifugal pumps operating under high-pressure conditions. The operating limits for pressure, temperature and toxicity of the flow product have been extended by some orders of magnitude. This is the logical result of the response to heightened safety environment requirements, and means that technical processes can now be implemented for the manufacture of new products. 

For the above example, a synthesis tool may alternately not generate a latch with asynchronous preset and clear, but direct the preset clear logic into the D-input of a simple latch. This is shown in the synthesized netlist that appears in Figure 2-43. 

Here is an example of a Mealy finite state machine. Variable MealyState holds the machine state, while NextState is used to pass information from the combinational logic always statement to the sequential logic always statement. Input Reset asynchronously resets the state to STO. 

Two flip-flops with asynchronous preset and clear are synthesized for the variable QuickBus. The variable LoadData is connected to the preset clear inputs of the flip-flops through other logic. When PreLoad is active (is 0) and LoadData changes, the outputs of the flip-flops are immediately affected because of the asynchronous data change. However in the design model, any change on LoadData has no effect on the output QuickBus. Thus there is a mismatch. 

An appealing property of Boolean networks is that they are inherently simple but emphasize generic network behavior. Nevertheless, the coarse abstraction to two possible activity values of genes and the synchronous state update are strong assumptions that may not always be justified. Various extensions of Boolean networks have been proposed to cope with these limitations. The formalism of generalized logical networks [Thomas and d Ari 1990] allows variables to have more than two values and transitions between states to occur asynchronously, whereas probabilistic Boolean networks allow uncertainty in the data and permit interactions between genes to be quantified [Shmulevich et al. 2002]. 

We describe an efficient implementation of a CTL model-checking algorithm based on alternating automata. We use this to check properties of an asynchronous micropipeline design described in the Rainbow framework, which operates at the micropipeline level and leads to compact models of the hardware. We also use alternating automata to characterise die expressive power and model-checking complexity for sub-logics of CTL. ... 

To be able to use mathematical proof techniques, some formalism for describing both specification and implementation has to be used. PTL, described in section 4, is one such formalism. In PTL, the specification is naturally described as an STG, but the implementation cannot be described directly as layout. Instead, transistor netlist extraction is typically used to get a switch-level description of the circuit layout. This type of description still has the disadvantage of containing too many electrical properties. A verification tool starting from this description must be able to understand domino logic, pseudo NMOS, dynamic storage elements, asynchronous circuits, etc. 

To reduce the chance of cross-link failures of redundant equipment, the redundant subsystems should be separated electrically and physically. The correct overall result may be obtained by voting the results obtained by each subsystem even when a component has failed or a subsystem is taken out of service for maintenance of the failed component. Because the voting logic itself necessitates common usage by all the subsystems, adequate and sufficient buffering should be used to ensure that the separation of the redundant equipment in the subsystems is maintained. Also, redundant subsystems should ran asynchronously. 

The requirements specifications of monitoring and control systems often demand high levels of performance from a computational system. For example, the computational task may involve real-world data acquisition, combinational or sequential logic functions, complex arithmetic calculations, and the generation of control outputs to the application plant. The computational response may be required within very tight time constraints, perhaps as part of a real-time schedule. The schedule may have to be maintained in the presence of asynchronous external inputs, such as operator commands or alarms. In addition, the system may have to perform safety functions or functions with safety implications. 

You are running DRC (check test) on the top level after integrating your ASIC. Finding that TC is inferring the a nchronous reset line as a clock and all the scan cells with asynchronous reset pins being classified as constant-logic black-box cells. 

G. Borriello. Synthesis of Asynchronous/Synchronous Control Logic. Proceedings of the IEEE International Symposium on Circuits and Systems (ISCAS 89), May 1989. 

With an asynchronous circuit, it is difficult to separate logical data and timing when performing circuit analyses. Generally, a circuit simulator is used for obtaining detailed wave forms. It takes the human designer much effort to analyze these wave forms and to identify and attempt to remove problems. Since this process requires much skill and time, it is considered impossible to automate. 

A final extension of the nton switch is to use the shadow logic to route packets of information [39], A particular application is the asynchronous transfer mode (ATM) data, which is transmitted in finite size packets. For ATM chip-to-chip interconnects, it is desirable to switch packets or blocks of information rather than individual fibers, which can be done by shadow logic. In this... 

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