Full case

Foreign, full case reports available a) As above... 

Published reports and other reports lacking full case reports... 

Figure 2-35 With full case synthesis directive no latches.

As the synthesized netlist shows, no latches are inferred for NextToggle when the full case synthesis directive is used. 

Caution, use of the full case directive can potentially lead to a functional mismatch between the design model and the synthesized netlist see Chapter 5 for such examples. 

It is necessary to specify the full case synthesis directive, otherwise latches are inferred for Address. Alternatively, an initial assignment to Address before the case statement can also be made to avoid latches no synthesis directive is then necessary. This is shown in the following always statement. 

Two flip-flops are inferred to hold the value of the variable MealyState with the specified state assignment. The default branch in the case statement can be avoided by specifying the case statement as full case , as shown next. 

In this case, no latches are inferred for Z and NextState since the full case synthesis directive states that no other case item values can occur. However, the preferred style for not inferring latches is to use the default branch. 

The problem with this approach is that since it is impractical to list all possible values an integer can take, to avoid latches either the default case branch must be specified or the full case synthesis directive must be used. Another problem with this approach is not good readability. 

The two synthesis directives we have seen so far, full case and parallel case, can potentially cause functional mismatches to occur between the design model and the synthesized netlist. The problem is that these directives are recognized only by a synthesis tool and not by a simulation tool. In either of the cases, if the designer is not careful in specifying the directive, mismatches can occur. 

Here is an example of a full case synthesis directive. 

The full case directive tells the synthesis tool that all possible values that can possibly occur in CurrentState have been listed and the value of Next-State is a don t-care for all other cases, and therefore, the synthesis tool should not generate latches for NextState. However this may not be true in simulation. It could happen that CurrentState for some reason, gets a value of 2 b00. In such a case, the case statement simulates as if NextState value is saved, but in the synthesized netlist, the value of NextState may not be saved. 

Recommendation Use caution when using the synthesis directives full case and parallel case. Use only if really necessary. 

The full case when the symmetry operations of the point group induce linear transformations amongst the basis functions. The matrices V are non-trivial orthogonaJ matrices. The centres are permuted and the basis functions are mixed by the transformations. 

Having seen how the implementation goes for the simplest possible case, we can proceed to the full case when symmetry operations induce linear combinations of basis functions on symmetry-equivalent centres. 

Business problem cases or "full case" interviews present the candidate with an open-ended business situation. Usually more complex and well developed than shorter estimation cases, these cases have no right answer and test your ability to think through issues to a conclusion that you can defend. 

Here are some examples of both estimation questions and full cases. It is best to work on these with friends, though it will also be helpful to just think about them yourself, and try to sketch out an issue tree, describing how you would break down and analyze each case. 

VHDL, by definition, requires that all the different values of an expression in a case statement be covered. However, this is not required in Verilog. If the user knows that all possible values of the case expression have been covered, one should use the Synopsys synthesis full case pragma. This prevents latches from being inferred due to not assigning values to a reg/signal under all possible conditions. 

Because the outcome of the Falsified Data case is unknown, the Plan and Do It stages cannot be fully analyzed. When the full case is reflected upon, we could, and would, do just that. 

In this chapter we use box outlines to summarize the tasks in each step. A full case study and references to related work are provided to clarify the detailed procedures. 

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