Delay operator

After resuscitation and hemodynamic stabilization, prompt surgical intervention is key in the treatment of NF. Delayed operative debridement increases mortality.21 Some... 

A common analytical tool for digital filters is the Z transform representation. As we said before, weTl define Z (Z to the minus 1) as a single sample of delay, and in fact, Z is sometimes called the Delay Operator. To transform a filter using the Z transform, simply capitalize all variables x andy, and replace all time indices ( - a) with the appropriate time delay operator Z" . Thus, the Z transformed version of Equation 3.3 would be written ... 

For Verilog, we refer to [7, chap 4], with the restriction that the " " delay operator is banned, and only blocking procedural assignments to registers are allowed. There exist some differences between the semantics of sequential statements in Verilog, on the one hand, and sequential assignments in VHDL, on the other. This will be illustrated by the examples in Figure 3. 

On the basis of all these experimental and theoretical results it can be concluded that for a FR of EFR-type the decay heat can be removed by natural convection only. The decay heat removal is functioning even under extreme conditions, e.g. delayed operation of DHX, loss of several DHR loops, reduced fluid level, inadverted opening of the air outlet dampers. 

First, an ASAP schedule is constructed, assuming infinite resources, and one cycle per operation. Then optimizations are applied, moving operations to other control steps to reduce the maximum number of operations of each type in any one control step, and grouping operations into functional units so as to have a minimum number of functional units. Uien the scheduler traverses the control step schedule, passing the operations in each control step to the data path allocator. The data path allocator tries to bind those operations using heuristics if it fails, the scheduler tries to delay operations until later control steps, and if that also fails, the user is notified that the resource constraints should be increased. 

Constraint Interactions. List scheduling operates by placing operators into successive control steps. Data-flow constraints, control-flow constraints, and minimum-time constraints can all have the effect of delaying the scheduling of an operator until these constraints are satisfied. If the delayed operator is also subject to a maximum-time constraint, then a possible conflict exists between the two constraints that may not be resolved by the CSTEP algorithm alone. 

External interfacing and synchronization. The ability to wait for the occurrence of a particular input event, i.e. assertion of a ready signal, is necessary to coordinate the actions between a set of concurrently execution modules. This interfacing is specified as eitha synchronization mechanisms or data-dependent loops in the input description, and it is modeled as unbounded delay operations in the synthesis fomulation. 

The shutdown valves shall close upon a demand. Several of them also have requirements with respect to closing time and some of them to maximum leakage rate in closed position. In total, 221 DU failures were observed for the shutdown valves from the six operational reviews. The DU failures mainly include the three failure modes fail to close on demand, leakage in closed position and delayed operation. The 11 CCF events registered involved the following failures ... 

DU failures (delayed operation) were due to poor design of hydraulic connections resulting in too long closing times. 

There are cases where the compiler is able to guarantee that this blocking is actually bounded (e.g. a delay operation). It may be possible to allow an implementation in this case to consider the tasklet not to be blocked. Nevertheless, in order to be consistent with the Ada standard, these operations are also considered to be potentially blocking [8, section 9.5.1]. 

Relative control synthesis. Relative scheduling complicates the task of ctxi-trol generation. When th are no data-dependent delay operations, the schedule consists of a single sequence of control steps that can be synthesized by traditional control strategies. For example, the schedule can be implemented as a microprogrammed controller or as a single finite-state machine. In the general case, however, these traditional control schemes are inadequate. 

Data-dependent delay operations. The execution delay of a vertex can be fixed or data-dependent. The latter type describes external synchronizations and loops. 

In traditional approaches, two vertices are disjoint if they are scheduled into different control steps. However, since our model supports data-dependent delay operations, these approaches cannot be used in general. Assume all operations have unbounded execution delay, then two operations are compatible if they have the same resource type and are joined by a directed path in the sequencing graph. 

Organization of chapter. This chapter presents the formulation and algorithms for relative scheduling. Our approach can be described in a nutshell as follows. In relative scheduling, we support both operations with fixed delay and operations with data-dependent delay data-dependent delay operations represent points of synchronization. We uniformly model both types of operations as vertices in the constraint graph model. We assume in this cluq)ter that resource binding and conflict resolution have been performed prior to scheduling. 

Scheduling problems are defined and solved on graphs with fixed delay operations. We extend this notion to graphs with data-dependent delay vertices. For a data-dependent delay vertex the execution delay is not known statically, and can assume any integer value from 0 to oo. For this reason, we define a subset of the vertices, called anchors, that serve as reference points for specifying the start times of operations. 

It is important to point out that the definition of anchors above applies to both unbounded delay operations, where the delay is not known statically, and bounded delay operations, wh e the delay is bounded but not fixed, i.e., an operation requiring either 2 or 3 cycles to execute, depending on some condition, is an example of an anchor with bounded delay. It is possible to treat a bounded-delay anchor as a fixed-delay non-anchor by assuming its worst-case delay, at the expense of possibly increasing the overall latency. 

We now consider the consistency of constraints in the presence of data-dependent delay vertices. Intuitively, the data-dependent delay vertices create time gaps that cannot be resolved statically. Depending on the execution profile of these operations, a timing constraint may or may not be satisfied by a given schedule. We extend the analysis by introducing the concept of well-posed versus ill-posed timing constraints, in the presence of data-dependent delay operations. 

This chapter describes algorithms for resource conflict resolution. Resource conflicts occur when multiple operations activate the same hardware resource simultaneously. When all operations in the hardware model have fixed execution delays, conflict resolution becomes part of the scheduling and resource binding tasks. In particular, operations scheduled to different control stq)s or belonging to mutually exclusive conditional branches can share their hardware resources. Consider for example the force-directed scheduling technique [PK89b]. Operations with similar resources are first scheduled to reduce their concurrency, then they are bound to hardware resources subject to this schedule. The binding step ensures that no resource conflicts will arise. This approach is, however, restricted to bounded delay operations. 

We make the following assumptions. First, the cardinality of the operation cluster must be greater than one ( C > 1), since othowise the ordering is trivial. Second, each vertex Cj C must either be a data-dependent delay operation (i.e. anchor) or have non-zero fixed execution delay, i.e. (c ) > 0. Note that registers have already been introduced prior to conflict resolution to latch the outputs of the shared resource. For example, the execution delay for shared calls to a combinational adder is 1 cycle because of the latching delay. 

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