1076_axb.html

basic exemple. Do an ADD of two 4 bits numbers

<p><b>B.160 named association:</b>  An association element in which the formal designator appears explicitly.  (&#167;  <a href = "1076_4.HTM#4.3.2.2"> 4.3.2.2 </a>  , &#167;  <a href = "1076_7.HTM#7.3.2"> 7.3.2 </a>  )
<p><b>B.161 named entity:</b>  An item associated with an identifier, character literal, or operator symbol as the result of an explicit or implicit declaration.  (&#167;4)  <i>See also</i> <b>name</b>.
<p><b>B.162 net:</b>  A collection of drivers, signals (including ports and implicit signals), conversion functions, and resolution functions that connect different processes.  Initialization of a net occurs after elaboration, and a net is updated during each simulation cycle.  (&#167;12, &#167;  <a href = "1076_12.HTM#12.1"> 12.1 </a>  , <i>&#167;</i>  <a href = "1076_12.HTM#12.6.2"> 12.6.2 </a>  )
<p><b>B.163 nonobject alias:</b>  An alias whose designator denotes some named entity other than an object.  (<i>&#167;</i>  <a href = "1076_4.HTM#4.3.3"> 4.3.3 </a>  , &#167;  <a href = "1076_4.HTM#4.3.3.2"> 4.3.3.2 </a>  )  <i>See also</i> <b>object alias</b>.
<p><b>B.164 nonpostponed process:</b>  An explicit or implicit process whose source statment does not contain the reserved word <b>postponed.  </b>When a nonpostponed process is resumed, it executes in the current simulation cycle.  Thus, nonpostponed processes have access to the current values of signals,whether or not those values are stable at the current model time.  (&#167;  <a href = "1076_9.HTM#9.2"> 9.2 </a>  )
<p><b>B.165 null array:</b>  Any of the discrete ranges in the index constraint of an array that define a null range.  (&#167;  <a href = "1076_3.HTM#3.2.1.1"> 3.2.1.1 </a>  )
<p><b>B.166 null range:</b>  A range that specifies an empty subset of values.  A range L <b>to</b> R is a null range if L <b>></b> R, and range L <b>downto</b> R is a null range if L <b>&lt;</b> R.  (&#167;  <a href = "1076_3.HTM#3.1"> 3.1 </a>  )
<p><b>B.167 null slice:</b>  A slice whose discrete range is a null range.(&#167;  <a href = "1076_6.HTM#6.5"> 6.5 </a>  )
<p><b>B.168 null waveform element:</b> A waveform element that is used to turn off a driver of a guarded signal.  (&#167;  <a href = "1076_8.HTM#8.4.1"> 8.4.1 </a>  )
<p><b>B.169 null transaction:</b>  A transaction produced by evaluating a null waveform element.  (&#167;  <a href = "1076_8.HTM#8.4.1"> 8.4.1 </a>  )
<p><b>B.170 numeric literal:</b>  An abstract literal, or a literal of a physical type.  (&#167;  <a href = "1076_7.HTM#7.3.1"> 7.3.1 </a>  )
<p><b>B.171 numeric type:</b>  An integer type, a floating point type, or a physical type.  (&#167;  <a href = "1076_3.HTM#3.1"> 3.1 </a>  )
<p><b>B.172 object:</b>  A named entity that has a value of a given type.  An object can be a constant, signal, variable, or file.  (&#167;  <a href = "1076_4.HTM#4.3.3"> 4.3.3 </a>  )
<p><b>B.173 object alias:</b>  An alias whose alias designator denotes an object(that is, a constant, signal, variable, or file).  (<i>&#167;</i>  <a href = "1076_4.HTM#4.3.3"> 4.3.3 </a>  , <i>&#167</i><i>;</i>  <a href = "1076_4.HTM#4.3.3.1"> 4.3.3.1 </a>  ) <i> See also</i> <b>nonobject alias</b>.
<p><b>B.174 overloaded:</b>  Identifiers or enumeration literals that denote two different named entities.  Enumeration literals, subprograms, and predefined operators may be overloaded.  At any place where an overloaded enumeration literal occurs in the text of a program, the type of the enumeration literal must be determinable from the context.  (&#167;  <a href = "1076_2.HTM#2.1"> 2.1 </a>  , &#167;  <a href = "1076_2.HTM#2.3"> 2.3 </a>  , &#167;  <a href = "1076_2.HTM#2.3.1"> 2.3.1 </a>  , &#167;  <a href = "1076_2.HTM#2.3.2"> 2.3.2 </a>  , <i>&#167;</i>  <a href = "1076_3.HTM#3.1.1"> 3.1.1 </a>  )
<p><b>B.175 parameter:</b>  A constant, signal, variable, or file declared in the interface list of a subprogram specification.  The characteristics of the class of objects to which a given parameter belongs are also characteristics of the parameter.  In addition, a parameter has an associated mode that specifies the direction of data flow allowed through the parameter.  (&#167;  <a href = "1076_2.HTM#2.1.1"> 2.1.1 </a>  , &#167;  <a href = "1076_2.HTM#2.1.1.1"> 2.1.1.1 </a>  , &#167;  <a href = "1076_2.HTM#2.1.1.2"> 2.1.1.2 </a>  , &#167;  <a href = "1076_2.HTM#2.1.1.3"> 2.1.1.3 </a>  , &#167;  <a href = "1076_2.HTM#2.3"> 2.3 </a>  , &#167;  <a href = "1076_2.HTM#2.6"> 2.6 </a>  )
<p><b>B.176 parameter interface list: </b>An interface list that declares the parameters for a subprogram.  It may contain interface constant declarations,interface signal declarations, interface variable declarations, interface file declarations, or any combination thereof.  (&#167;  <a href = "1076_4.HTM#4.3.2.1"> 4.3.2.1 </a>  )
<p><b>B.177 parameter type profile:</b>  Two formal parameter lists that have the same number of parameters, and at each parameter position the corresponding parameters have the same base type.  (&#167;  <a href = "1076_2.HTM#2.3"> 2.3 </a>  )
<p><b>B.178 parameter and result type profile: </b> Two subprograms that have the same parameter type profile, and either both are functions with the same result base type, or neither of the two is a function.  (&#167;  <a href = "1076_2.HTM#2.3"> 2.3 </a>  )
<p><b>B.179 parent:</b>  A process or a subprogram that contains a procedure call statement for a given procedure or for a parent of the given procedure.(&#167;  <a href = "1076_2.HTM#2.2"> 2.2 </a>  )
<p><b>B.180 passive process: </b> A process statement where neither the process itself, nor any procedure of which the process is a parent, contains a signal assignment statement.  (&#167;  <a href = "1076_9.HTM#9.2"> 9.2 </a>  )
<p><b>B.181 physical literal:</b>  A numeric literal of a physical type.(&#167;  <a href = "1076_3.HTM#3.1.3"> 3.1.3 </a>  )
<p><b>B.182 physical type:</b>  A numeric scalar type that is used to represent measurements of some quantity.  Each value of a physical type has a position number that is an integer value.  Any value of a physical type is an integral multiple of the primary unit of measurement for that type.  (<i>&#167;</i>  <a href = "1076_3.HTM#3.1"> 3.1 </a>  , &#167;  <a href = "1076_3.HTM#3.1.3"> 3.1.3 </a>  )
<p><b>B.183 port:</b>  A channel for dynamic communication between a block and its environment.  A signal declared in the interface list of an entity declaration,in the header of a block statement, or in the interface list of a component declaration. In addition to the characteristics of signals, ports also have an associated mode; the mode constrains the directions of data flow allowed through the port.  (<i>&#167;</i><i>  <a href = "1076_1.HTM#1.1.1.2"> 1.1.1.2 </a>  </i>, &#167;  <a href = "1076_4.HTM#4.3.1.2"> 4.3.1.2 </a>  )
<p><b>B.184 port interface list:</b>  An interface list that declares the inputs and outputs of a block, component, or design entity.  It consists entirely of interface signal declarations.  (&#167;  <a href = "1076_1.HTM#1.1.1"> 1.1.1 </a>  , <i>&#167;</i><i>  <a href = "1076_1.HTM#1.1.1.2"> 1.1.1.2 </a>  </i>, &#167;  <a href = "1076_4.HTM#4.3.2.1"> 4.3.2.1 </a>  , &#167;  <a href = "1076_4.HTM#4.3.2.2"> 4.3.2.2 </a>  , &#167;  <a href = "1076_9.HTM#9.1"> 9.1 </a>  )
<p><b>B.185 positional association:</b>  An association element that does not contain an explicit appearance of the formal designator.  An actual designator at a given position in an association list corresponds to the interface element at the same position in the interface list.  (&#167;  <a href = "1076_4.HTM#4.3.2.2"> 4.3.2.2 </a>  , &#167;  <a href = "1076_7.HTM#7.3.2"> 7.3.2 </a>  )
<p><b>B.186 postponed process: </b>An explicit or implicit process whose source statement contains the reserved word <b>postponed. </b> When a postponed process is resumed, it does not execute until the final simulation cycle at the current modeled time.  Thus, a postponed process accesses the values of signals that are the "stable" values at the current simulated time.  (&#167;  <a href = "1076_9.HTM#9.2"> 9.2 </a>  ) 
<p><b>B.187 predefined operators:</b>  Implicitly defined operators that operate on the predefined types.  Every predefined operator is a pure function.  No predefined operators have named formal parameters; therefore, named association may not be used when invoking a predefined operation.  (&#167;  <a href = "1076_7.HTM#7.2"> 7.2 </a>  , &#167;  <a href = "1076_14.HTM#14.2"> 14.2 </a>  )
<p><b>B.188 primary:</b>  One of the elements making up an expression.  Each primary has a value and a type.  (&#167;  <a href = "1076_7.HTM#7.1"> 7.1 </a>  )
<p><b>B.189 projected output waveform: </b>A sequence of one or more transactions representing the current and projected future values of the driver.(&#167;  <a href = "1076_12.HTM#12.6.1"> 12.6.1 </a>  )
<p><b>B.190 pulse rejection limit:</b>  The threshold time limit for which a signal value whose duration is greater than the limit will be propagated.  A pulse rejection limit is specified by the reserved word <b>reject</b> in an inertially delayed signal assignment statement.  (&#167;  <a href = "1076_8.HTM#8.4"> 8.4 </a>  )
<p><b>B.191 pure function:</b>  A function that returns the same value each time it is called with the same values as actual parameters.  An <i>impure</i> function may return a different value each time it is called, even when different calls have the same actual parameter values.  (&#167;  <a href = "1076_2.HTM#2.1"> 2.1 </a>  )
<p><b>B.192 quiet:</b>  In a given simulation cycle, a signal that is not active.(&#167;  <a href = "1076_12.HTM#12.6.2"> 12.6.2 </a>  )
<p><b>B.193 range:</b> A specified subset of values of a scalar type.  (&#167;  <a href = "1076_3.HTM#3.1"> 3.1 </a>  )<i>See also</i> <b>ascending range</b>, <b>belong</b> (to a range),<b>descending range</b>, <b>lower bound</b>, and <b>upper bound</b>.
<p><b>B.194 range constraint:</b>  A construct that specifies the range of values in a type.  A range constraint is <i>compatible</i> with a subtype if each bound of the range belongs to the subtype or if the range constraint defines a null range.  The direction of a range constraint is the same as the direction of its range.  (<i>&#167;</i>  <a href = "1076_3.HTM#3.1"> 3.1 </a>  , <i>&#167;</i>  <a href = "1076_3.HTM#3.1.2"> 3.1.2 </a>  , &#167;  <a href = "1076_3.HTM#3.1.3"> 3.1.3 </a>  , &#167;  <a href = "1076_3.HTM#3.1.4"> 3.1.4 </a>  )
<p><b>B.195 read:</b>  The value of an object is said to be <i>read</i> when its value is referenced or when certain of its attributes are referenced.(&#167;  <a href = "1076_4.HTM#4.3.2"> 4.3.2 </a>  )
<p><b>B.196 real literal:</b>  An abstract literal of the type <i>universal_real</i> that contains a base point.  (&#167;  <a href = "1076_13.HTM#13.4"> 13.4 </a>  )
<p><b>B.197 record type:  </b>A composite type whose values consist of named elements.  (<i>&#167;</i>  <a href = "1076_3.HTM#3.2.2"> 3.2.2 </a>  , &#167;  <a href = "1076_7.HTM#7.3.2.1"> 7.3.2.1 </a>  )
<p><b>B.198 reference:</b>  Access to a named entity.  Every appearance of a designator (a name, character literal, or operator symbol) is a reference to the named entity denoted by the designator, unless the designator appears in a library clause or use clause.  (&#167;  <a href = "1076_10.HTM#10.4"> 10.4 </a>  , &#167;  <a href = "1076_11.HTM#11.2"> 11.2 </a>  )
<p><b>B.199 register: </b> A kind of guarded signal that retains its last driven value when all of its drivers are turned off.  (&#167;  <a href = "1076_4.HTM#4.3.1.2"> 4.3.1.2 </a>  )
<p><b>B.200 regular structure:</b>  Instances of one or more components arranged and interconnected (via signals) in a repetitive way.  Each instance may have characteristics that depend upon its position within the group of instances.  Regular structures may be represented through the use of the generate statement.  (&#167;  <a href = "1076_9.HTM#9.7"> 9.7 </a>  )
<p><b>B.201 resolution:</b>  The process of determining the resolved value of a resolved signal based on the values of multiple sources for that signal.(&#167;  <a href = "1076_2.HTM#2.4"> 2.4 </a>  , &#167;  <a href = "1076_4.HTM#4.3.1.2"> 4.3.1.2 </a>  )
<p><b>B.202 resolution function:</b>  A user-defined function that computes the resolved value of a resolved signal.  (&#167;  <a href = "1076_2.HTM#2.4"> 2.4 </a>  , &#167;  <a href = "1076_4.HTM#4.3.1.2"> 4.3.1.2 </a>  )
<p><b>B.203 resolution limit:</b>  The primary unit of type TIME (by default, 1femtosecond).  Any TIME value whose absolute value is smaller than this limit is truncated to zero (0) time units.  (&#167;  <a href = "1076_3.HTM#3.1.3.1"> 3.1.3.1 </a>  )
<p><b>B.204 resolved signal:</b>  A signal that has an associated resolution function.  (&#167;  <a href = "1076_4.HTM#4.3.1.2"> 4.3.1.2 </a>  )
<p><b>B.205 resolved value:</b>  The output of the resolution function associated with the resolved signal, which is determined as a function of the collection of inputs from the multiple sources of the signal.  (<i></i><i>&#167;</i>  <a href = "1076_2.HTM#2.4"> 2.4 </a>  <i>, </i>&#167;  <a href = "1076_4.HTM#4.3.1.2"> 4.3.1.2 </a>  )
<p><b>B.206 resource library:</b>  A library containing library units that are referenced within the design unit being analyzed.  (&#167;  <a href = "1076_11.HTM#11.2"> 11.2 </a>  )
<p><b>B.207 result subtype: </b> The subtype of the returned value of a function.(&#167;  <a href = "1076_2.HTM#2.1"> 2.1 </a>  )
<p><b>B.208 resume:  </b>The action of a wait statement upon an enclosing process when the conditions on which the wait statement is waiting are satisfied.  If the enclosing process is a nonpostponed process, the process will subsequently execute during the current simulation cycle.  Otherwise, the process