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<title>VHDL LRM- Introduction</title>
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<pre> { waveform <b>when</b> condition <b>else</b> }
waveform [ <b>when</b> condition ]
configuration_declaration ::= <b>[§<a href = "1076_1.HTM#1.3"> 1.3</a>]</b>
<b>configuration</b> identifier <b>of</b> <i>entity</i>_name <b>is</b>
configuration_declarative_part
block_configuration
<b>end</b> [ <b>configuration</b> ] [ <i>configuration</i>_simple_name ] ;
configuration_declarative_item ::= <b>[§<a href = "1076_1.HTM#1.3"> 1.3</a>]</b>
use_clause
| attribute_specification
| group_declaration
configuration_declarative_part ::= <b>[§<a href = "1076_1.HTM#1.3"> 1.3</a>]</b>
{ configuration_declarative_item }
configuration_item ::= <b>[§<a href = "1076_1.HTM#1.3.1"> 1.3.1</a>]</b>
block_configuration
| component_configuration
configuration_specification ::= <b>[§<a href = "1076_5.HTM#5.2"> 5.2</a>]</b>
<b>for</b> component_specification binding_indication ;
constant_declaration ::= <b>[§<a href = "1076_4.HTM#4.3.1.1"> 4.3.1.1</a>]</b>
<b>constant</b> identifier_list : subtype_indication [ := expression ] ;
constrained_array_definition ::= <b>[§<a href = "1076_3.HTM#3.2.1"> 3.2.1</a>]</b>
<b>array</b> index_constraint <b>of</b> <i>element</i>_subtype_indication
constraint ::= <b>[§<a href = "1076_4.HTM#4.2"> 4.2</a>]</b>
range_constraint
| index_constraint
context_clause ::= { context_item } <b>[§<a href = "1076_11.HTM#11.3"> 11.3</a>]</b>
context_item ::= <b>[§<a href = "1076_11.HTM#11.3"> 11.3</a>]</b>
library_clause
| use_clause
decimal_literal ::= integer [ . integer ] [ exponent ] <b>[§<a href = "1076_13.HTM#13.4.1"> 13.4.1</a>]</b>
declaration ::= <b>[§ 4]</b>
type_declaration
| subtype_declaration
| object_declaration
| interface_declaration
| alias_declaration
| attribute_declaration
| component_declaration
| group_template_declaration
| group_declaration
| entity_declaration
| configuration_declaration
| subprogram_declaration
| package_declaration
delay_mechanism ::= <b>[§<a href = "1076_8.HTM#8.4"> 8.4</a>]</b>
<b>transport</b>
| [ <b>reject</b> <i>time</i>_expression ] <b>inertial</b>
design_file ::= design_unit { design_unit } <b>[§<a href = "1076_11.HTM#11.1"> 11.1</a>]</b>
design_unit ::= context_clause library_unit <b>[§<a href = "1076_11.HTM#11.1"> 11.1</a>]</b>
designator ::= identifier | operator_symbol <b>[§<a href = "1076_2.HTM#2.1"> 2.1</a>]</b>
direction ::= <b>to</b> | <b>downto</b> <b>[§<a href = "1076_3.HTM#3.1"> 3.1</a>]</b>
disconnection_specification ::= <b>[§<a href = "1076_5.HTM#5.3"> 5.3</a>]</b>
</pre>
<pre> <b>disconnect </b>guarded_signal_specification <b>after </b><i>time</i>_expression ;
discrete_range ::= <i>discrete</i>_subtype_indication | range <b>[§<a href = "1076_3.HTM#3.2.1"> 3.2.1</a>]</b>
element_association ::= <b>[§<a href = "1076_7.HTM#7.3.2"> 7.3.2</a>]</b>
[ choices => ] expression
element_declaration ::= <b>[§<a href = "1076_3.HTM#3.2.2"> 3.2.2</a>]</b>
identifier_list : element_subtype_definition ;
element_subtype_definition ::= subtype_indication <b>[§<a href = "1076_3.HTM#3.2.2"> 3.2.2</a>]</b>
entity_aspect ::= <b>[§<a href = "1076_5.HTM#5.2.1.1"> 5.2.1.1</a>]</b>
<b>entity</b> <i>entity</i>_name [ ( <i>architecture</i>_identifier) ]
| <b>configuration</b> <i>configuration</i>_name
| <b>open</b>
entity_class ::= <b>[§<a href = "1076_5.HTM#5.1"> 5.1</a>]</b>
<b>entity</b> | <b>architecture</b> | <b>configuration</b>
| <b>procedure</b> | <b>function</b> | <b>package</b>
| <b>type</b> | <b>subtype</b> | <b>constant</b>
| <b>signal</b> | <b>variable</b> | <b>component</b>
| <b>label</b> | <b>literal</b> | <b>units</b>
| <b>group</b> | <b>file</b>
entity_class_entry ::= entity_class [ <> ] <b>[§<a href = "1076_4.HTM#4.6"> 4.6</a>]</b>
entity_class_entry_list ::= <b>[§<a href = "1076_4.HTM#4.6"> 4.6</a>]</b>
entity_class_entry { , entity_class_entry }
entity_declaration ::= <b>[§<a href = "1076_1.HTM#1.1"> 1.1</a>]</b>
<b>entity</b> identifier <b>is</b>
entity_header
entity_declarative_part
[ <b>begin</b>
entity_statement_part ]
<b>end</b> [ <b>entity</b> ] [ <i>entity</i>_simple_name ] ;
entity_declarative_item ::= <b>[§<a href = "1076_1.HTM#1.1.2"> 1.1.2</a>]</b>
subprogram_declaration
| subprogram_body
| type_declaration
| subtype_declaration
| constant_declaration
| signal_declaration
| <i>shared</i>_variable_declaration
| file_declaration
| alias_declaration
| attribute_declaration
| attribute_specification
| disconnection_specification
| use_clause
| group_template_declaration
| group_declaration
entity_declarative_part ::= <b>[§<a href = "1076_1.HTM#1.1.2"> 1.1.2</a>]</b>
{ entity_declarative_item }
entity_designator ::= entity_tag [ signature ] <b>[§<a href = "1076_5.HTM#5.1"> 5.1</a>]</b>
entity_header ::= <b>[§<a href = "1076_1.HTM#1.1.1"> 1.1.1</a>]</b>
[ <i>formal</i>_generic_clause ]
[ <i>formal</i>_port_clause ]
entity_name_list ::= <b>[§<a href = "1076_5.HTM#5.1"> 5.1</a>]</b>
entity_designator { , entity_designator }
| <b>others</b>
| <b>all</b>
entity_specification ::= <b>[§<a href = "1076_5.HTM#5.1"> 5.1</a>]</b>
entity_name_list : entity_class
entity_statement ::= <b>[§<a href = "1076_1.HTM#1.1.3"> 1.1.3</a>]</b>
</pre>
<pre> concurrent_assertion_statement
| <i>passive</i>_concurrent_procedure_call_statement
| <i>passive</i>_process_statement
entity_statement_part ::= <b>[§<a href = "1076_1.HTM#1.1.3"> 1.1.3</a>]</b>
{ entity_statement }
entity_tag ::= simple_name | character_literal | operator_symbol <b>[§</b> <b> <a href = "1076_5.HTM#5.1"> 5.1</a>]</b>
enumeration_literal ::= identifier | character_literal <b>[§<a href = "1076_3.HTM#3.1.1"> 3.1.1</a>]</b>
enumeration_type_definition ::= <b>[§<a href = "1076_3.HTM#3.1.1"> 3.1.1</a>]</b>
( enumeration_literal { , enumeration_literal } )
exit_statement ::= <b>[§<a href = "1076_8.HTM#8.11"> 8.11</a>]</b>
[ label : ] <b>exit</b> [ <i>loop</i>_label ] [ <b>when</b> condition ] ;
exponent ::= E [ + ] integer | E - integer <b>[§<a href = "1076_13.HTM#13.4.1"> 13.4.1</a>]</b>
expression ::= <b>[§<a href = "1076_7.HTM#7.1"> 7.1</a>]</b>
relation { <b>and</b> relation }
| relation { <b>or</b> relation }
| relation { <b>xor</b> relation }
| relation [ <b>nand</b> relation ]
| relation [ <b>nor</b> relation ]
| relation { <b>xnor</b> relation }
extended_digit ::= digit | letter <b>[§<a href = "1076_13.HTM#13.4.2"> 13.4.2</a>]</b>
extended_identifier ::= \ graphic_character { graphic_character } \ <b>[§<a href = "1076_13.HTM#13.3.2"> 13.3.2</a>]</b>
factor ::= <b>[§<a href = "1076_7.HTM#7.1"> 7.1</a>]</b>
primary [ ** primary ]
| <b>abs</b> primary
| <b>not</b> primary
file_declaration ::= <b>[§<a href = "1076_4.HTM#4.3.1.4"> 4.3.1.4</a>]</b>
<b>file</b> identifier_list : subtype_indication [ file_open_information ] ;
file_logical_name ::= <i>string</i>_expression <b>[§<a href = "1076_4.HTM#4.3.1.4"> 4.3.1.4</a>]</b>
file_open_information ::= <b>[§<a href = "1076_4.HTM#4.3.1.4"> 4.3.1.4</a>]</b>
[ <b>open</b> <i>file_open_kind</i>_expression ] <b>is</b> file_logical_name
file_type_definition ::= <b>[§<a href = "1076_3.HTM#3.4"> 3.4</a>]</b>
<b>file</b> <b>of</b> type_mark
floating_type_definition ::= range_constraint <b>[§<a href = "1076_3.HTM#3.1.4"> 3.1.4</a>]</b>
formal_designator ::= <b>[§<a href = "1076_4.HTM#4.3.2.2"> 4.3.2.2</a>]</b>
<i>generic</i>_name
| <i>port</i>_name
| <i>parameter</i>_name
formal_parameter_list ::= <i>parameter</i>_interface_list <b>[§<a href = "1076_2.HTM#2.1.1"> 2.1.1</a>]</b>
formal_part ::= <b>[§<a href = "1076_4.HTM#4.3.2.2"> 4.3.2.2</a>]</b>
formal_designator
| <i>function</i>_name ( formal_designator )
| type_mark ( formal_designator )
full_type_declaration ::= <b>[§<a href = "1076_4.HTM#4.1"> 4.1</a>]</b>
<b>type</b> identifier <b>is</b> type_definition ;
function_call ::= <b>[§<a href = "1076_7.HTM#7.3.3"> 7.3.3</a>]</b>
</pre>
<pre> <i>function</i>_name [ ( actual_parameter_part ) ]
generate_statement ::= <b>[§<a href = "1076_9.HTM#9.7"> 9.7</a>]</b>
<i>generate</i>_label :
generation_scheme <b>generate</b>
[ { block_declarative_item }
<b>begin</b> ]
{ concurrent_statement }
<b>end generate</b> [ <i>generate</i>_label ] ;
generation_scheme ::= <b>[§<a href = "1076_9.HTM#9.7"> 9.7</a>]</b>
<b>for</b> <i>generate</i>_parameter_specification
| <b>if</b> condition
generic_clause ::= <b>[§<a href = "1076_1.HTM#1.1.1"> 1.1.1</a>]</b>
<b>generic</b> ( generic_list ) ;
generic_list ::= <i>generic</i>_interface_list <b>[§<a href = "1076_1.HTM#1.1.1.1"> 1.1.1.1</a>]</b>
generic_map_aspect ::= <b>[§<a href = "1076_5.HTM#5.2.1.2"> 5.2.1.2</a>]</b>
<b>generic map</b> ( <i>generic</i>_association_list )
graphic_character ::= <b>[§<a href = "1076_13.HTM#13.1"> 13.1</a>]</b>
basic_graphic_character | lower_case_letter | other_special_character
group_constituent ::= name | character_literal <b>[§<a href = "1076_4.HTM#4.7"> 4.7</a>]</b>
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