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Xilinx Synthesis Technology User Guide

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Table 6-4 Objects<br />

VHDL Language Support<br />

Constant Declaration Supported (deferred constants are not<br />

supported)<br />

Signal Declaration Supported (“register” or “bus” type<br />

signals are not supported)<br />

Variable Declaration Supported<br />

File Declaration Unsupported<br />

Alias Declaration Supported<br />

Attribute Declaration Supported for some attributes, otherwise<br />

skipped (see the “Design Constraints”<br />

chapter)<br />

Component Declaration Supported<br />

Table 6-5 Specifications<br />

Attribute Only supported for some predefined attributes:<br />

HIGH, LOW, LEFT, RIGHT, RANGE,<br />

REVERSE_RANGE, LENGTH, POS,<br />

ASCENDING, EVENT, LAST_VALUE.<br />

Otherwise, ignored.<br />

Configuration Supported only with the “all” clause for<br />

instances list. If no clause is added, XST looks<br />

for the entity/architecture compiled in the<br />

default library.<br />

Disconnection Unsupported<br />

Table 6-6 Names<br />

Simple Names Supported<br />

Selected Names Supported<br />

Indexed Names Supported<br />

Slice Names Supported (including dynamic ranges)<br />

XST <strong>User</strong> <strong>Guide</strong> 6-43

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