Blocking assignment

There is another restriction on using both blocking and non-blocking assignments in a single model for synthesis. 

A target cannot be assigned using a blocking assignment... 

Blocking assignments mirror the dataflow in a combinational circuit. Consider the following always statement. 

All the assignments are blocking assignments. Statements within the sequential block imply to compute the value of TM first, then execute the second statement, assign to 77V, then go to third statement, assign to TO, and so on. This mimics the dataflow through the combinational logic. 

These problems can simply be avoided by using blocking assignments when modeling combinational logic and are therefore recommended. 

Let us first consider what happens if blocking assignments are exclusively used for modeling sequential logic. Consider the following two always statements. 

What if the assignment and reading of a variable all occur in the same clocked always statement In such a case, blocking assignments may be used. 

Therefore, the recommendation is to use non-blocking assignments for variables that are read outside of the always statement in which they are assigned. Additionally, for variables that are assigned and used only within an always statement, use blocking assignments. 

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