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<h1><a name="AnnexC">Annex C</a></h1>
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<h1>Potentially nonportable constructs</h1>
<h1>(informative)</h1>
<p>This annex lists those VHDL constructs whose use may result in nonportable descriptions. A description is considered portable if it
<ul>
<p>a) Compiles, elaborates, initializes, and simulates to termination of the simulation cycle on all conformant implementations, and
<p>b) The time-variant state of all signals and variables in the description are the same at all times during the simulation
</ul>
<p>under the condition that the same stimuli are applied at the same times to the description. The stimuli applied to a model include the values supplied to generics and ports at the root of the design hierarchy of the model, if any.
<p>Note that the content of files generated by a description are not part of the state of the description, but that the content of files consumed by a description are part of the state of the description.
<p>The use of the following constructs may lead to nonportable VHDL descriptions:
<ul>
<p>-- Resolution functions that do not treat all inputs symmetrically.
<p>-- The comparison of floating point values.
<p>-- Events on floating-point-valued signals.
<p>-- The use of explicit type conversion to convert floating point values to integer values.
<p>-- Any value that does not fall within the minimum guaranteed range for the type.
<p>-- The use of architectures and subprogram bodies implemented via the foreign language interface (the 'FOREIGN attribute).
<p>-- Processes that communicate via file I/O, including TEXTIO.
<p>-- Impure functions.
<p>-- Linkage ports.
<p>-- Ports and generics in the root of a design hierarchy.
<p>-- Use of a time resolution greater than fs.
<p>-- Shared variables.
<p>-- Procedure calls passing a single object of an array or record type to multiple formals where at least one of the formals is of mode <b>out</b> or <b>inout</b>.
<p>-- Models that depend on a particular format of T'Image.
<p>-- Declarations of integer or physical types that have a secondary unit whose position number is outside of the range -(2**31-1) <b>to</b> 2**31-1.
<p>-- The predefined attributes 'INSTANCE_NAME or 'PATH_NAME, if the behavior of the model is dependent on the values returned by the attributes.
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