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Unformatted text preview: LANGUAGE REFERENCE MANUAL IEEE Std P1076a-1999 2000/D3 Annex C Potentially nonportable constructs (informative) This annex lists those VHDL constructs whose use may result in nonportable descriptions. A description is considered portable if it a) b) Compiles, elaborates, initializes, and simulates to termination of the simulation cycle on all conformant implementations, and The time-variant state of all signals and variables in the description are the same at all times during the simulation 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. 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. The use of the following constructs may lead to nonportable VHDL descriptions: -- -- -- -- -- -- -- -- -- -- -- -- Annex C Copyright 2000, IEEE. All rights reserved. This is an unapproved IEEE Standards Draft, subject to change. Resolution functions that do not treat all inputs symmetrically. The comparison of floating-point values. Events on floating-point-valued signals. The use of explicit type conversion to convert floating-point values to integer values. Any value that does not fall within the minimum guaranteed range for the type. The use of architectures and subprogram bodies implemented via the foreign language interface (the 'FOREIGN attribute). Processes that communicate via file I/O, including TEXTIO. Impure functions. Linkage ports. Ports and generics in the root of a design hierarchy. Use of a time resolution greater than fs. Shared variables. 257 IEEE Std P1076a-1999 2000/D3 IEEE STANDARD VHDL -- -- -- -- 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 out or inout. Models that depend on a particular format of T'Image IMAGE1. Declarations of integer or physical types that have a secondary unit whose position number is outside of the range -(2**31-1) to 2**31-1. The predefined attributes 'INSTANCE_NAME or 'PATH_NAME, if the behavior of the model is dependent on the values returned by the attributes. 1. Correction noted by Lance Thompson. 258 Copyright 2000, IEEE. All rights reserved. This is an unapproved IEEE Standards Draft, subject to change. Annex C ...
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This note was uploaded on 09/09/2009 for the course EECS 318 taught by Professor Saab during the Fall '01 term at Case Western.

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